acpi_pad mwait usage

[Peter Zijlstra]

Hi Len, Rafeal,

I stumbled over acpi_pad (yuck! ;-), but noticed that you don't set the
task in polling mode while using mwait. This means we'll still happily
send an IPI to wake you up.

A little something like the below should do; you might even be able to
remove the smp_mb() but since it is completely undocumented (another
fail) I couldn't tell if the implied barrier in
current_set_polling_and_test() suffices to replace it, so I left it.

If it compiles and works; change it to a proper SOB:

Maybe-Signed-off-by: Peter Zijlstra <pet...@infradead.org>
---
drivers/acpi/acpi_pad.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
index fc6008fbce35..e9126efe7786 100644
--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -195,8 +195,10 @@ static int power_saving_thread(void *data)

__monitor((void *)&current_thread_info()->flags, 0, 0);
smp_mb();
- if (!need_resched())
+ if (!current_set_polling_and_test()) {
__mwait(power_saving_mwait_eax, 1);
+ __current_clr_polling();
+ }

start_critical_timings();
if (lapic_marked_unstable)
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[Peter Zijlstra]

On Tue, Nov 19, 2013 at 10:00:19AM +0100, Peter Zijlstra wrote:
> Hi Len, Rafeal,
>
> I stumbled over acpi_pad (yuck! ;-), but noticed that you don't set the
> task in polling mode while using mwait. This means we'll still happily
> send an IPI to wake you up.
>
> A little something like the below should do; you might even be able to
> remove the smp_mb() but since it is completely undocumented (another
> fail) I couldn't tell if the implied barrier in
> current_set_polling_and_test() suffices to replace it, so I left it.
>
> If it compiles and works; change it to a proper SOB:
>
> Maybe-Signed-off-by: Peter Zijlstra <pet...@infradead.org>

Of course one such driver is insufficient and you lot needed a second;
same issue:

---
drivers/thermal/intel_powerclamp.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c
index 8f181b3f842b..d8111e1ac62e 100644
--- a/drivers/thermal/intel_powerclamp.c
+++ b/drivers/thermal/intel_powerclamp.c
@@ -439,8 +439,11 @@ static int clamp_thread(void *arg)
local_touch_nmi();
stop_critical_timings();

__monitor((void *)&current_thread_info()->flags, 0, 0);

- cpu_relax(); /* allow HT sibling to run */
- __mwait(eax, ecx);
+ if (!current_set_polling_and_test()) {
+ cpu_relax(); /* allow HT sibling to run */
+ __mwait(eax, ecx);
+ __current_clr_polling();
+ }
start_critical_timings();
atomic_inc(&idle_wakeup_counter);

[Peter Zijlstra]

People seem to delight in writing wrong and broken mwait idle routines;
collapse the lot.

This leaves mwait_play_dead() the sole remaining user of __mwait() and
new __mwait() users are probably doing it wrong.

Also remove __sti_mwait() as its unused.

Signed-off-by: Peter Zijlstra <pet...@infradead.org>
---

Mike, does this cure your core2?

arch/x86/include/asm/mwait.h | 42 ++++++++++++++++++++++++++++++++++++++
arch/x86/include/asm/processor.h | 23 ---------------------
arch/x86/kernel/acpi/cstate.c | 23 ---------------------
drivers/acpi/acpi_pad.c | 5 +----
drivers/acpi/processor_idle.c | 15 --------------
drivers/idle/intel_idle.c | 8 +-------
drivers/thermal/intel_powerclamp.c | 4 +---
7 files changed, 45 insertions(+), 75 deletions(-)

diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
index 2f366d0ac6b4..80014dade987 100644
--- a/arch/x86/include/asm/mwait.h
+++ b/arch/x86/include/asm/mwait.h
@@ -1,6 +1,8 @@
#ifndef _ASM_X86_MWAIT_H
#define _ASM_X86_MWAIT_H

+#include <linux/sched.h>
+
#define MWAIT_SUBSTATE_MASK 0xf
#define MWAIT_CSTATE_MASK 0xf
#define MWAIT_SUBSTATE_SIZE 4
@@ -13,4 +15,44 @@

#define MWAIT_ECX_INTERRUPT_BREAK 0x1

+static inline void __monitor(const void *eax, unsigned long ecx,
+ unsigned long edx)
+{
+ /* "monitor %eax, %ecx, %edx;" */
+ asm volatile(".byte 0x0f, 0x01, 0xc8;"
+ :: "a" (eax), "c" (ecx), "d"(edx));
+}
+
+static inline void __mwait(unsigned long eax, unsigned long ecx)
+{
+ /* "mwait %eax, %ecx;" */
+ asm volatile(".byte 0x0f, 0x01, 0xc9;"
+ :: "a" (eax), "c" (ecx));
+}
+
+/*
+ * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
+ * which can obviate IPI to trigger checking of need_resched.
+ * We execute MONITOR against need_resched and enter optimized wait state
+ * through MWAIT. Whenever someone changes need_resched, we would be woken
+ * up from MWAIT (without an IPI).
+ *
+ * New with Core Duo processors, MWAIT can take some hints based on CPU
+ * capability.
+ */
+static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx)
+{
+ if (need_resched())
+ return;
+
+ if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
+ clflush((void *)&current_thread_info()->flags);
+
+ __monitor((void *)&current_thread_info()->flags, 0, 0);
+ if (!current_set_polling_and_test())
+ __mwait(eax, ecx);
+
+ __current_clr_polling();
+}
+
#endif /* _ASM_X86_MWAIT_H */
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 7b034a4057f9..24821f5768bc 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -700,29 +700,6 @@ static inline void sync_core(void)
#endif
}

-static inline void __monitor(const void *eax, unsigned long ecx,
- unsigned long edx)
-{
- /* "monitor %eax, %ecx, %edx;" */
- asm volatile(".byte 0x0f, 0x01, 0xc8;"
- :: "a" (eax), "c" (ecx), "d"(edx));
-}
-
-static inline void __mwait(unsigned long eax, unsigned long ecx)
-{
- /* "mwait %eax, %ecx;" */
- asm volatile(".byte 0x0f, 0x01, 0xc9;"
- :: "a" (eax), "c" (ecx));
-}
-
-static inline void __sti_mwait(unsigned long eax, unsigned long ecx)
-{
- trace_hardirqs_on();
- /* "mwait %eax, %ecx;" */
- asm volatile("sti; .byte 0x0f, 0x01, 0xc9;"
- :: "a" (eax), "c" (ecx));
-}
-
extern void select_idle_routine(const struct cpuinfo_x86 *c);
extern void init_amd_e400_c1e_mask(void);

diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
index d2b7f27781bc..e69182fd01cf 100644
--- a/arch/x86/kernel/acpi/cstate.c
+++ b/arch/x86/kernel/acpi/cstate.c
@@ -150,29 +150,6 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu,
}
EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe);

-/*
- * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
- * which can obviate IPI to trigger checking of need_resched.
- * We execute MONITOR against need_resched and enter optimized wait state
- * through MWAIT. Whenever someone changes need_resched, we would be woken
- * up from MWAIT (without an IPI).
- *
- * New with Core Duo processors, MWAIT can take some hints based on CPU
- * capability.
- */
-void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
-{
- if (!need_resched()) {
- if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
- clflush((void *)&current_thread_info()->flags);
-
- __monitor((void *)&current_thread_info()->flags, 0, 0);
- smp_mb();
- if (!need_resched())
- __mwait(ax, cx);
- }
-}
-
void acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cx)
{
unsigned int cpu = smp_processor_id();
diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
index fc6008fbce35..509452a62f96 100644
--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -193,10 +193,7 @@ static int power_saving_thread(void *data)
CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
stop_critical_timings();

- __monitor((void *)&current_thread_info()->flags, 0, 0);
- smp_mb();
- if (!need_resched())
- __mwait(power_saving_mwait_eax, 1);
+ mwait_idle_with_hints(power_saving_mwait_eax, 1);

start_critical_timings();
if (lapic_marked_unstable)
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 644516d9bde6..f90c56c8379e 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -727,11 +727,6 @@ static int acpi_idle_enter_c1(struct cpuidle_device *dev,
if (unlikely(!pr))
return -EINVAL;

- if (cx->entry_method == ACPI_CSTATE_FFH) {
- if (current_set_polling_and_test())
- return -EINVAL;
- }
-
lapic_timer_state_broadcast(pr, cx, 1);
acpi_idle_do_entry(cx);

@@ -785,11 +780,6 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
if (unlikely(!pr))
return -EINVAL;

- if (cx->entry_method == ACPI_CSTATE_FFH) {
- if (current_set_polling_and_test())
- return -EINVAL;
- }
-
/*
* Must be done before busmaster disable as we might need to
* access HPET !
@@ -841,11 +831,6 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
}
}

- if (cx->entry_method == ACPI_CSTATE_FFH) {
- if (current_set_polling_and_test())
- return -EINVAL;
- }
-
acpi_unlazy_tlb(smp_processor_id());

/* Tell the scheduler that we are going deep-idle: */
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 3226ce98fb18..3b56d76a5bca 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -359,13 +359,7 @@ static int intel_idle(struct cpuidle_device *dev,
if (!(lapic_timer_reliable_states & (1 << (cstate))))
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);

- if (!current_set_polling_and_test()) {
-
- __monitor((void *)&current_thread_info()->flags, 0, 0);
- smp_mb();
- if (!need_resched())
- __mwait(eax, ecx);
- }
+ mwait_idle_with_hints(eax, ecx);

if (!(lapic_timer_reliable_states & (1 << (cstate))))
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c
index 8f181b3f842b..e8275f2df9af 100644
--- a/drivers/thermal/intel_powerclamp.c
+++ b/drivers/thermal/intel_powerclamp.c
@@ -438,9 +438,7 @@ static int clamp_thread(void *arg)
*/
local_touch_nmi();
stop_critical_timings();
- __monitor((void *)&current_thread_info()->flags, 0, 0);

- cpu_relax(); /* allow HT sibling to run */
- __mwait(eax, ecx);

+ mwait_idle_with_hints(eax, ecx);

[Rafael J. Wysocki]

On Tuesday, November 19, 2013 12:31:53 PM Peter Zijlstra wrote:
> People seem to delight in writing wrong and broken mwait idle routines;
> collapse the lot.
>
> This leaves mwait_play_dead() the sole remaining user of __mwait() and
> new __mwait() users are probably doing it wrong.
>
> Also remove __sti_mwait() as its unused.
>
> Signed-off-by: Peter Zijlstra <pet...@infradead.org>

For the ACPI part:

Acked-by: Rafael J. Wysocki <rafael.j...@intel.com>

I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.

[Mike Galbraith]

On Tue, 2013-11-19 at 12:31 +0100, Peter Zijlstra wrote:
> People seem to delight in writing wrong and broken mwait idle routines;
> collapse the lot.
>
> This leaves mwait_play_dead() the sole remaining user of __mwait() and
> new __mwait() users are probably doing it wrong.
>
> Also remove __sti_mwait() as its unused.
>
> Signed-off-by: Peter Zijlstra <pet...@infradead.org>
> ---
>
> Mike, does this cure your core2?

Nope. Maybe an acpi/bios thingy on this box since diags that fired on
lappy during boot did not fire on desktop, and both are core2 booting
same kernel. I kinda suspect I'll either be stuck with default_idle or
have to resurrect mwait_idle and carry it locally if I want the thing to
work well. Guess I'll find out if/when I have time to squabble with it.

Meanwhile, desktop box works fine modulo benchmarks, lappy works fine
too, modulo max_cstate=1 scaring mwait_idle_with_hints away, which I
don't care about much. Neither box is wonderful at rt testing where I
usually boot max_cstate=1, both just became a bit _less_ wonderful :)

-Mike

[Arjan van de Ven]

> diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c
> index 8f181b3f842b..e8275f2df9af 100644
> --- a/drivers/thermal/intel_powerclamp.c
> +++ b/drivers/thermal/intel_powerclamp.c
> @@ -438,9 +438,7 @@ static int clamp_thread(void *arg)
> */
> local_touch_nmi();
> stop_critical_timings();
> - __monitor((void *)&current_thread_info()->flags, 0, 0);
> - cpu_relax(); /* allow HT sibling to run */
> - __mwait(eax, ecx);
> + mwait_idle_with_hints(eax, ecx);
> start_critical_timings();
> atomic_inc(&idle_wakeup_counter);
> }
>

hmm I take it that mwait_idle_with_hints is the one that also checks need_resched() ?
if so... powerclamp may not want to use that (the whole point is to NOT give the cpu
to tasks!)

[Peter Zijlstra]

On Tue, Nov 19, 2013 at 06:22:43AM -0800, Arjan van de Ven wrote:
> >diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c
> >index 8f181b3f842b..e8275f2df9af 100644
> >--- a/drivers/thermal/intel_powerclamp.c
> >+++ b/drivers/thermal/intel_powerclamp.c
> >@@ -438,9 +438,7 @@ static int clamp_thread(void *arg)
> > */
> > local_touch_nmi();
> > stop_critical_timings();
> >- __monitor((void *)&current_thread_info()->flags, 0, 0);
> >- cpu_relax(); /* allow HT sibling to run */
> >- __mwait(eax, ecx);
> >+ mwait_idle_with_hints(eax, ecx);
> > start_critical_timings();
> > atomic_inc(&idle_wakeup_counter);
> > }
> >
>
> hmm I take it that mwait_idle_with_hints is the one that also checks need_resched() ?
> if so... powerclamp may not want to use that (the whole point is to NOT give the cpu
> to tasks!)

Of course, you're very much not getting something that wins from
stop_machine or a fifo-99 task.

[Peter Zijlstra]

On Tue, Nov 19, 2013 at 06:22:43AM -0800, Arjan van de Ven wrote:

> >diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c
> >index 8f181b3f842b..e8275f2df9af 100644
> >--- a/drivers/thermal/intel_powerclamp.c
> >+++ b/drivers/thermal/intel_powerclamp.c
> >@@ -438,9 +438,7 @@ static int clamp_thread(void *arg)
> > */
> > local_touch_nmi();
> > stop_critical_timings();
> >- __monitor((void *)&current_thread_info()->flags, 0, 0);
> >- cpu_relax(); /* allow HT sibling to run */
> >- __mwait(eax, ecx);
> >+ mwait_idle_with_hints(eax, ecx);
> > start_critical_timings();
> > atomic_inc(&idle_wakeup_counter);
> > }
> >
>
> hmm I take it that mwait_idle_with_hints is the one that also checks need_resched() ?
> if so... powerclamp may not want to use that (the whole point is to NOT give the cpu
> to tasks!)

That said, that drive is completely wrecked. It uses
preempt_enable_no_resched() wrong too, it has uncommented barriers..

Dude, wtf are you guys smoking?

[Peter Zijlstra]

On Tue, Nov 19, 2013 at 03:51:43PM +0100, Peter Zijlstra wrote:
> That said, that drive is completely wrecked. It uses
> preempt_enable_no_resched() wrong too, it has uncommented barriers..
>
> Dude, wtf are you guys smoking?

---
Subject: sched: Take away preempt_enable_no_resched() and friends from modules

There is no way in hell modules are going to play preemption tricks like
this.

Cc: elieze...@linux.intel.com
Cc: ar...@linux.intel.com
Reviewed-by: Thomas Gleixner <tg...@linutronix.de>

Signed-off-by: Peter Zijlstra <pet...@infradead.org>
---

drivers/thermal/intel_powerclamp.c | 2 +-
include/linux/preempt.h | 8 +++++++-
include/net/busy_poll.h | 15 +++------------
3 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c
index 8f181b3f842b..0a12ddc2eb4c 100644
--- a/drivers/thermal/intel_powerclamp.c
+++ b/drivers/thermal/intel_powerclamp.c
@@ -445,7 +445,7 @@ static int clamp_thread(void *arg)
atomic_inc(&idle_wakeup_counter);
}
tick_nohz_idle_exit();
- preempt_enable_no_resched();
+ preempt_enable();
}
del_timer_sync(&wakeup_timer);
clear_bit(cpunr, cpu_clamping_mask);
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index a3d9dc8c2c00..3ed2b5335ab4 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -64,7 +64,7 @@ do { \
} while (0)

#else
-#define preempt_enable() preempt_enable_no_resched()
+#define preempt_enable() sched_preempt_enable_no_resched()
#define preempt_check_resched() do { } while (0)
#endif

@@ -116,6 +116,12 @@ do { \

#endif /* CONFIG_PREEMPT_COUNT */

+#ifdef MODULE
+#undef preempt_enable_no_resched
+#undef preempt_enable_no_resched_notrace
+#undef preempt_check_resched
+#endif
+
#ifdef CONFIG_PREEMPT_NOTIFIERS

struct preempt_notifier;
diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
index 829627d7b846..756827a86c2d 100644
--- a/include/net/busy_poll.h
+++ b/include/net/busy_poll.h
@@ -42,27 +42,18 @@ static inline bool net_busy_loop_on(void)
return sysctl_net_busy_poll;
}

-/* a wrapper to make debug_smp_processor_id() happy
- * we can use sched_clock() because we don't care much about precision
- * we only care that the average is bounded
- */
-#ifdef CONFIG_DEBUG_PREEMPT
static inline u64 busy_loop_us_clock(void)
{
u64 rc;

+ /* XXX with interrupts enabled sched_clock() can return utter garbage */
+
preempt_disable_notrace();
rc = sched_clock();
- preempt_enable_no_resched_notrace();
+ preempt_enable_notrace();

return rc >> 10;
}
-#else /* CONFIG_DEBUG_PREEMPT */
-static inline u64 busy_loop_us_clock(void)
-{
- return sched_clock() >> 10;
-}
-#endif /* CONFIG_DEBUG_PREEMPT */

static inline unsigned long sk_busy_loop_end_time(struct sock *sk)
{

[Jacob Pan]

On Tue, 19 Nov 2013 16:13:38 +0100
Peter Zijlstra <pet...@infradead.org> wrote:

> On Tue, Nov 19, 2013 at 03:51:43PM +0100, Peter Zijlstra wrote:
> > That said, that drive is completely wrecked. It uses
> > preempt_enable_no_resched() wrong too, it has uncommented barriers..
> >
> > Dude, wtf are you guys smoking?
>

I applied this patch on top of upstream kernel (801a760) and found out
my machine completely failed to enter idle when nothing is running.
turbostate shows 100% C0. ftrace shows kernel coming in and out of idle
frequently.

Both ACPI idle and intel_idle behaves the same way. I have to do the
following change to allow entering C-states again.

diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
index 80014da..b51d1e1 100644
--- a/arch/x86/include/asm/mwait.h
+++ b/arch/x86/include/asm/mwait.h
@@ -49,10 +49,8 @@ static inline void mwait_idle_with_hints(unsigned
long eax, unsigned long ecx) clflush((void
*)&current_thread_info()->flags);

__monitor((void *)&current_thread_info()->flags, 0, 0);

- if (!current_set_polling_and_test())
+ if (!need_resched())
__mwait(eax, ecx);
-
- __current_clr_polling();
}

#endif /* _ASM_X86_MWAIT_H */

Did i miss any other patches?

Jacob

[Jacob Pan]

[Peter Zijlstra]

That doesn't make any sense; current_set_polling_and_test() returns the
same thing need_resched() does.

But you're right, intel_idle resides 100% in C0 and acpi_idle has 100%
C1 residency... most weird.

/me goes prod at it

[Peter Zijlstra]

On Wed, Nov 20, 2013 at 11:28:03AM +0100, Peter Zijlstra wrote:
> On Tue, Nov 19, 2013 at 01:06:30PM -0800, Jacob Pan wrote:
> > I applied this patch on top of upstream kernel (801a760) and found out
> > my machine completely failed to enter idle when nothing is running.
> > turbostate shows 100% C0. ftrace shows kernel coming in and out of idle
> > frequently.
> >
> > Both ACPI idle and intel_idle behaves the same way. I have to do the
> > following change to allow entering C-states again.

> That doesn't make any sense; current_set_polling_and_test() returns the
> same thing need_resched() does.
>
> But you're right, intel_idle resides 100% in C0 and acpi_idle has 100%
> C1 residency... most weird.

So pretty silly actually; you cannot do a store (any store) in between
monitor and mwait.

The below version seems to work properly again with both acpi_idle and
intel_idle.

Now to go make that preempt_disable_no_resched cleanup compile.. :-)

---
Subject: x86, acpi, idle: Restructure the mwait idle routines
From: Peter Zijlstra <pet...@infradead.org>
Date: Tue, 19 Nov 2013 12:31:53 +0100

People seem to delight in writing wrong and broken mwait idle routines;
collapse the lot.

This leaves mwait_play_dead() the sole remaining user of __mwait() and
new __mwait() users are probably doing it wrong.

Also remove __sti_mwait() as its unused.

Cc: ar...@linux.intel.com
Cc: jacob....@linux.intel.com
Cc: Mike Galbraith <bitb...@online.de>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Thomas Gleixner <tg...@linutronix.de>
Cc: h...@zytor.com
Cc: le...@kernel.org
Cc: shaoh...@intel.com
Cc: rui....@intel.com

Acked-by: Rafael J. Wysocki <rafael.j...@intel.com>

Signed-off-by: Peter Zijlstra <pet...@infradead.org>
---

arch/x86/include/asm/mwait.h | 40 +++++++++++++++++++++++++++++++++++++

arch/x86/include/asm/processor.h | 23 ---------------------
arch/x86/kernel/acpi/cstate.c | 23 ---------------------

drivers/acpi/acpi_pad.c | 5 ----
drivers/acpi/processor_idle.c | 15 -------------
drivers/idle/intel_idle.c | 8 -------
drivers/thermal/intel_powerclamp.c | 4 ---
7 files changed, 43 insertions(+), 75 deletions(-)

--- a/arch/x86/include/asm/mwait.h
+++ b/arch/x86/include/asm/mwait.h

@@ -1,6 +1,8 @@
#ifndef _ASM_X86_MWAIT_H
#define _ASM_X86_MWAIT_H

+#include <linux/sched.h>
+
#define MWAIT_SUBSTATE_MASK 0xf
#define MWAIT_CSTATE_MASK 0xf
#define MWAIT_SUBSTATE_SIZE 4

@@ -13,4 +15,42 @@

+static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx)
+{
+ if (!current_set_polling_and_test()) {

+ if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
+ clflush((void *)&current_thread_info()->flags);
+

+ __monitor((void *)&current_thread_info()->flags, 0, 0);
+ if (!need_resched())

+ __mwait(eax, ecx);
+ }
+ __current_clr_polling();
+}
+
#endif /* _ASM_X86_MWAIT_H */

--- a/arch/x86/kernel/acpi/cstate.c
+++ b/arch/x86/kernel/acpi/cstate.c
@@ -150,29 +150,6 @@ int acpi_processor_ffh_cstate_probe(unsi
}

--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -193,10 +193,7 @@ static int power_saving_thread(void *dat

CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
stop_critical_timings();

- __monitor((void *)&current_thread_info()->flags, 0, 0);
- smp_mb();
- if (!need_resched())
- __mwait(power_saving_mwait_eax, 1);
+ mwait_idle_with_hints(power_saving_mwait_eax, 1);

start_critical_timings();
if (lapic_marked_unstable)

--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -727,11 +727,6 @@ static int acpi_idle_enter_c1(struct cpu

if (unlikely(!pr))
return -EINVAL;

- if (cx->entry_method == ACPI_CSTATE_FFH) {
- if (current_set_polling_and_test())
- return -EINVAL;
- }
-
lapic_timer_state_broadcast(pr, cx, 1);
acpi_idle_do_entry(cx);

@@ -785,11 +780,6 @@ static int acpi_idle_enter_simple(struct

if (unlikely(!pr))
return -EINVAL;

- if (cx->entry_method == ACPI_CSTATE_FFH) {
- if (current_set_polling_and_test())
- return -EINVAL;
- }
-
/*
* Must be done before busmaster disable as we might need to
* access HPET !
@@ -841,11 +831,6 @@ static int acpi_idle_enter_bm(struct cpu
}
}

- if (cx->entry_method == ACPI_CSTATE_FFH) {
- if (current_set_polling_and_test())
- return -EINVAL;
- }
-
acpi_unlazy_tlb(smp_processor_id());

/* Tell the scheduler that we are going deep-idle: */

--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -359,13 +359,7 @@ static int intel_idle(struct cpuidle_dev

if (!(lapic_timer_reliable_states & (1 << (cstate))))
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);

- if (!current_set_polling_and_test()) {
-
- __monitor((void *)&current_thread_info()->flags, 0, 0);
- smp_mb();
- if (!need_resched())
- __mwait(eax, ecx);
- }
+ mwait_idle_with_hints(eax, ecx);

if (!(lapic_timer_reliable_states & (1 << (cstate))))
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);

--- a/drivers/thermal/intel_powerclamp.c
+++ b/drivers/thermal/intel_powerclamp.c

@@ -438,9 +438,7 @@ static int clamp_thread(void *arg)
*/
local_touch_nmi();
stop_critical_timings();
- __monitor((void *)&current_thread_info()->flags, 0, 0);
- cpu_relax(); /* allow HT sibling to run */
- __mwait(eax, ecx);
+ mwait_idle_with_hints(eax, ecx);
start_critical_timings();
atomic_inc(&idle_wakeup_counter);
}

[Arjan van de Ven]

On 11/20/2013 2:58 AM, Peter Zijlstra wrote:
> On Wed, Nov 20, 2013 at 11:28:03AM +0100, Peter Zijlstra wrote:
>> On Tue, Nov 19, 2013 at 01:06:30PM -0800, Jacob Pan wrote:
>>> I applied this patch on top of upstream kernel (801a760) and found out
>>> my machine completely failed to enter idle when nothing is running.
>>> turbostate shows 100% C0. ftrace shows kernel coming in and out of idle
>>> frequently.
>>>
>>> Both ACPI idle and intel_idle behaves the same way. I have to do the
>>> following change to allow entering C-states again.
>
>> That doesn't make any sense; current_set_polling_and_test() returns the
>> same thing need_resched() does.
>>
>> But you're right, intel_idle resides 100% in C0 and acpi_idle has 100%
>> C1 residency... most weird.
>
> So pretty silly actually; you cannot do a store (any store) in between
> monitor and mwait.

you can
just not to the cacheline you are watching (or things that alias with that)

[Peter Zijlstra]

On Wed, Nov 20, 2013 at 08:24:47AM -0800, Arjan van de Ven wrote:
> On 11/20/2013 2:58 AM, Peter Zijlstra wrote:
> >So pretty silly actually; you cannot do a store (any store) in between
> >monitor and mwait.
>
> you can
> just not to the cacheline you are watching (or things that alias with that)

Ah indeed, the thread_info::status is in the same cacheline.

[Arjan van de Ven]

On 11/20/2013 8:33 AM, Peter Zijlstra wrote:
> On Wed, Nov 20, 2013 at 08:24:47AM -0800, Arjan van de Ven wrote:
>> On 11/20/2013 2:58 AM, Peter Zijlstra wrote:
>>> So pretty silly actually; you cannot do a store (any store) in between
>>> monitor and mwait.
>>
>> you can
>> just not to the cacheline you are watching (or things that alias with that)
>
> Ah indeed, the thread_info::status is in the same cacheline.
>

you told it to wake on any write to that cacheline
and then you write to it ;-)

[tip-bot for Peter Zijlstra]

Commit-ID: 29fc2f66b552770909591d89ee87ab8690d67e61
Gitweb: http://git.kernel.org/tip/29fc2f66b552770909591d89ee87ab8690d67e61
Author: Peter Zijlstra <pet...@infradead.org>
AuthorDate: Tue, 19 Nov 2013 16:13:38 +0100
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Sun, 12 Jan 2014 14:50:37 +0100

sched, net: Fixup busy_loop_us_clock()

The only valid use of preempt_enable_no_resched() is if the very next
line is schedule() or if we know preemption cannot actually be enabled
by that statement due to known more preempt_count 'refs'.

This busy_poll stuff looks to be completely and utterly broken,
sched_clock() can return utter garbage with interrupts enabled (rare
but still) and it can drift unbounded between CPUs.

This means that if you get preempted/migrated and your new CPU is
years behind on the previous CPU we get to busy spin for a _very_ long
time.

There is a _REASON_ sched_clock() warns about preemptability -
papering over it with a preempt_disable()/preempt_enable_no_resched()
is just terminal brain damage on so many levels.

Replace sched_clock() usage with local_clock() which has a bounded
drift between CPUs (<2 jiffies).

There is a further problem with the entire busy wait poll thing in
that the spin time is additive to the syscall timeout, not inclusive.

Reviewed-by: Thomas Gleixner <tg...@linutronix.de>
Signed-off-by: Peter Zijlstra <pet...@infradead.org>

Cc: David S. Miller <da...@davemloft.net>
Cc: rui....@intel.com

Cc: jacob....@linux.intel.com
Cc: Mike Galbraith <bitb...@online.de>

Cc: h...@zytor.com
Cc: Arjan van de Ven <ar...@linux.intel.com>
Cc: le...@kernel.org
Cc: r...@rjwysocki.net
Cc: Eliezer Tamir <elieze...@linux.intel.com>
Cc: Linus Torvalds <torv...@linux-foundation.org>
Cc: Andrew Morton <ak...@linux-foundation.org>
Link: http://lkml.kernel.org/r/2013111915...@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
include/net/busy_poll.h | 19 +------------------
1 file changed, 1 insertion(+), 18 deletions(-)

diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
index 829627d..1d67fb6 100644
--- a/include/net/busy_poll.h
+++ b/include/net/busy_poll.h
@@ -42,27 +42,10 @@ static inline bool net_busy_loop_on(void)

return sysctl_net_busy_poll;
}

-/* a wrapper to make debug_smp_processor_id() happy
- * we can use sched_clock() because we don't care much about precision
- * we only care that the average is bounded
- */
-#ifdef CONFIG_DEBUG_PREEMPT

-static inline u64 busy_loop_us_clock(void)
-{

- u64 rc;
-
- preempt_disable_notrace();
- rc = sched_clock();
- preempt_enable_no_resched_notrace();
-
- return rc >> 10;
-}
-#else /* CONFIG_DEBUG_PREEMPT */
static inline u64 busy_loop_us_clock(void)
{
- return sched_clock() >> 10;
+ return local_clock() >> 10;

[tip-bot for Peter Zijlstra]

Commit-ID: c795eb55e74041a4b1e46a82bb07d8bd513fb066
Gitweb: http://git.kernel.org/tip/c795eb55e74041a4b1e46a82bb07d8bd513fb066

Author: Peter Zijlstra <pet...@infradead.org>
AuthorDate: Tue, 19 Nov 2013 16:13:38 +0100
Committer: Ingo Molnar <mi...@kernel.org>

CommitDate: Sun, 12 Jan 2014 10:48:24 +0100

sched/preempt, locking: Rework local_bh_{dis,en}able()

Currently local_bh_disable() is out-of-line for no apparent reason.
So inline it to save a few cycles on call/return nonsense, the
function body is a single add on x86 (a few loads and store extra on
load/store archs).

Also expose two new local_bh functions:

__local_bh_{dis,en}able_ip(unsigned long ip, unsigned int cnt);

Which implement the actual local_bh_{dis,en}able() behaviour.

The next patch uses the exposed @cnt argument to optimize bh lock
functions.

With build fixes from Jacob Pan.

Cc: r...@rjwysocki.net

Cc: rui....@intel.com
Cc: jacob....@linux.intel.com
Cc: Mike Galbraith <bitb...@online.de>
Cc: h...@zytor.com
Cc: Arjan van de Ven <ar...@linux.intel.com>
Cc: le...@kernel.org

Reviewed-by: Thomas Gleixner <tg...@linutronix.de>
Signed-off-by: Peter Zijlstra <pet...@infradead.org>

Link: http://lkml.kernel.org/r/2013111915...@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---

include/linux/bottom_half.h | 32 +++++++++++++++++++++++++++++---
include/linux/hardirq.h | 1 +
include/linux/preempt_mask.h | 1 -
kernel/softirq.c | 35 ++++++-----------------------------
4 files changed, 36 insertions(+), 33 deletions(-)

diff --git a/include/linux/bottom_half.h b/include/linux/bottom_half.h
index 27b1bcf..86c12c9 100644
--- a/include/linux/bottom_half.h
+++ b/include/linux/bottom_half.h
@@ -1,9 +1,35 @@
#ifndef _LINUX_BH_H
#define _LINUX_BH_H

-extern void local_bh_disable(void);
+#include <linux/preempt.h>
+#include <linux/preempt_mask.h>
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+extern void __local_bh_disable_ip(unsigned long ip, unsigned int cnt);
+#else
+static __always_inline void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
+{
+ preempt_count_add(cnt);
+ barrier();
+}
+#endif
+
+static inline void local_bh_disable(void)
+{
+ __local_bh_disable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET);
+}
+
extern void _local_bh_enable(void);
-extern void local_bh_enable(void);
-extern void local_bh_enable_ip(unsigned long ip);
+extern void __local_bh_enable_ip(unsigned long ip, unsigned int cnt);
+
+static inline void local_bh_enable_ip(unsigned long ip)
+{
+ __local_bh_enable_ip(ip, SOFTIRQ_DISABLE_OFFSET);
+}
+
+static inline void local_bh_enable(void)
+{
+ __local_bh_enable_ip(_THIS_IP_, SOFTIRQ_DISABLE_OFFSET);
+}

#endif /* _LINUX_BH_H */
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index d9cf963..12d5f97 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -5,6 +5,7 @@
#include <linux/lockdep.h>
#include <linux/ftrace_irq.h>
#include <linux/vtime.h>
+#include <asm/hardirq.h>


extern void synchronize_irq(unsigned int irq);
diff --git a/include/linux/preempt_mask.h b/include/linux/preempt_mask.h
index d169820..30820ec 100644
--- a/include/linux/preempt_mask.h
+++ b/include/linux/preempt_mask.h
@@ -2,7 +2,6 @@
#define LINUX_PREEMPT_MASK_H

#include <linux/preempt.h>
-#include <asm/hardirq.h>

/*
* We put the hardirq and softirq counter into the preemption
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 9a4500e..2a4b5f4 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -89,7 +89,7 @@ static void wakeup_softirqd(void)
* where hardirqs are disabled legitimately:
*/
#ifdef CONFIG_TRACE_IRQFLAGS
-static void __local_bh_disable(unsigned long ip, unsigned int cnt)
+void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
{
unsigned long flags;

@@ -114,21 +114,9 @@ static void __local_bh_disable(unsigned long ip, unsigned int cnt)
if (preempt_count() == cnt)
trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
}
-#else /* !CONFIG_TRACE_IRQFLAGS */
-static inline void __local_bh_disable(unsigned long ip, unsigned int cnt)
-{
- preempt_count_add(cnt);
- barrier();
-}
+EXPORT_SYMBOL(__local_bh_disable_ip);
#endif /* CONFIG_TRACE_IRQFLAGS */

-void local_bh_disable(void)
-{
- __local_bh_disable(_RET_IP_, SOFTIRQ_DISABLE_OFFSET);
-}
-
-EXPORT_SYMBOL(local_bh_disable);
-
static void __local_bh_enable(unsigned int cnt)
{
WARN_ON_ONCE(!irqs_disabled());
@@ -151,7 +139,7 @@ void _local_bh_enable(void)

EXPORT_SYMBOL(_local_bh_enable);

-static inline void _local_bh_enable_ip(unsigned long ip)
+void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
{
WARN_ON_ONCE(in_irq() || irqs_disabled());
#ifdef CONFIG_TRACE_IRQFLAGS
@@ -166,7 +154,7 @@ static inline void _local_bh_enable_ip(unsigned long ip)
* Keep preemption disabled until we are done with
* softirq processing:
*/
- preempt_count_sub(SOFTIRQ_DISABLE_OFFSET - 1);
+ preempt_count_sub(cnt - 1);

if (unlikely(!in_interrupt() && local_softirq_pending())) {
/*
@@ -182,18 +170,7 @@ static inline void _local_bh_enable_ip(unsigned long ip)
#endif
preempt_check_resched();
}
-
-void local_bh_enable(void)
-{
- _local_bh_enable_ip(_RET_IP_);
-}
-EXPORT_SYMBOL(local_bh_enable);
-
-void local_bh_enable_ip(unsigned long ip)
-{
- _local_bh_enable_ip(ip);
-}
-EXPORT_SYMBOL(local_bh_enable_ip);
+EXPORT_SYMBOL(__local_bh_enable_ip);

/*
* We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
@@ -264,7 +241,7 @@ asmlinkage void __do_softirq(void)
pending = local_softirq_pending();
account_irq_enter_time(current);

- __local_bh_disable(_RET_IP_, SOFTIRQ_OFFSET);
+ __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
in_hardirq = lockdep_softirq_start();

cpu = smp_processor_id();

[tip-bot for Peter Zijlstra]

Commit-ID: 3a5cd0b09443edb2f960497928de047e9c8ab848
Gitweb: http://git.kernel.org/tip/3a5cd0b09443edb2f960497928de047e9c8ab848

Author: Peter Zijlstra <pet...@infradead.org>
AuthorDate: Tue, 19 Nov 2013 16:13:38 +0100
Committer: Ingo Molnar <mi...@kernel.org>

CommitDate: Sun, 12 Jan 2014 14:50:35 +0100

sched, net: Clean up preempt_enable_no_resched() abuse

The only valid use of preempt_enable_no_resched() is if the very next
line is schedule() or if we know preemption cannot actually be enabled
by that statement due to known more preempt_count 'refs'.

Reviewed-by: Thomas Gleixner <tg...@linutronix.de>
Signed-off-by: Peter Zijlstra <pet...@infradead.org>

Cc: r...@rjwysocki.net
Cc: Eliezer Tamir <elieze...@linux.intel.com>

Cc: David S. Miller <da...@davemloft.net>

Cc: rui....@intel.com
Cc: jacob....@linux.intel.com
Cc: Mike Galbraith <bitb...@online.de>
Cc: h...@zytor.com
Cc: Arjan van de Ven <ar...@linux.intel.com>
Cc: le...@kernel.org

Cc: Linus Torvalds <torv...@linux-foundation.org>
Cc: Andrew Morton <ak...@linux-foundation.org>

Link: http://lkml.kernel.org/r/2013111915...@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---

net/ipv4/tcp.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c4638e6..82de786 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1623,11 +1623,11 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
(len > sysctl_tcp_dma_copybreak) && !(flags & MSG_PEEK) &&
!sysctl_tcp_low_latency &&
net_dma_find_channel()) {
- preempt_enable_no_resched();
+ preempt_enable();
tp->ucopy.pinned_list =
dma_pin_iovec_pages(msg->msg_iov, len);
} else {
- preempt_enable_no_resched();
+ preempt_enable();
}
}
#endif

[tip-bot for Peter Zijlstra]

Commit-ID: 9ea4c380066fbe23fe0da7f4abfabc444f2467f4
Gitweb: http://git.kernel.org/tip/9ea4c380066fbe23fe0da7f4abfabc444f2467f4

Author: Peter Zijlstra <pet...@infradead.org>
AuthorDate: Tue, 19 Nov 2013 16:13:38 +0100
Committer: Ingo Molnar <mi...@kernel.org>

CommitDate: Mon, 13 Jan 2014 13:47:36 +0100

locking: Optimize lock_bh functions

Currently all _bh_ lock functions do two preempt_count operations:

local_bh_disable();
preempt_disable();

and for the unlock:

preempt_enable_no_resched();
local_bh_enable();

Since its a waste of perfectly good cycles to modify the same variable
twice when you can do it in one go; use the new
__local_bh_{dis,en}able_ip() functions that allow us to provide a
preempt_count value to add/sub.

So define SOFTIRQ_LOCK_OFFSET as the offset a _bh_ lock needs to
add/sub to be done in one go.

As a bonus it gets rid of the preempt_enable_no_resched() usage.

This reduces a 1000 loops of:

spin_lock_bh(&bh_lock);
spin_unlock_bh(&bh_lock);

from 53596 cycles to 51995 cycles. I didn't do enough measurements to
say for absolute sure that the result is significant but the the few
runs I did for each suggest it is so.

Reviewed-by: Thomas Gleixner <tg...@linutronix.de>
Signed-off-by: Peter Zijlstra <pet...@infradead.org>

Cc: jacob....@linux.intel.com
Cc: Mike Galbraith <bitb...@online.de>
Cc: h...@zytor.com
Cc: Arjan van de Ven <ar...@linux.intel.com>
Cc: le...@kernel.org

Cc: r...@rjwysocki.net
Cc: rui....@intel.com

Cc: Linus Torvalds <torv...@linux-foundation.org>
Cc: Andrew Morton <ak...@linux-foundation.org>
Link: http://lkml.kernel.org/r/2013111915...@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---

include/linux/preempt_mask.h | 15 +++++++++++++++
include/linux/rwlock_api_smp.h | 12 ++++--------
include/linux/spinlock_api_smp.h | 12 ++++--------
include/linux/spinlock_api_up.h | 16 +++++++++++-----
kernel/softirq.c | 4 ++--
5 files changed, 36 insertions(+), 23 deletions(-)

diff --git a/include/linux/preempt_mask.h b/include/linux/preempt_mask.h
index d169820..b8d96bc 100644
--- a/include/linux/preempt_mask.h
+++ b/include/linux/preempt_mask.h
@@ -79,6 +79,21 @@
#endif

/*
+ * The preempt_count offset needed for things like:
+ *
+ * spin_lock_bh()
+ *
+ * Which need to disable both preemption (CONFIG_PREEMPT_COUNT) and
+ * softirqs, such that unlock sequences of:
+ *
+ * spin_unlock();
+ * local_bh_enable();
+ *
+ * Work as expected.
+ */
+#define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_CHECK_OFFSET)
+
+/*
* Are we running in atomic context? WARNING: this macro cannot
* always detect atomic context; in particular, it cannot know about
* held spinlocks in non-preemptible kernels. Thus it should not be
diff --git a/include/linux/rwlock_api_smp.h b/include/linux/rwlock_api_smp.h
index 9c9f049..5b9b84b 100644
--- a/include/linux/rwlock_api_smp.h
+++ b/include/linux/rwlock_api_smp.h
@@ -172,8 +172,7 @@ static inline void __raw_read_lock_irq(rwlock_t *lock)

static inline void __raw_read_lock_bh(rwlock_t *lock)
{
- local_bh_disable();
- preempt_disable();
+ __local_bh_disable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
rwlock_acquire_read(&lock->dep_map, 0, 0, _RET_IP_);
LOCK_CONTENDED(lock, do_raw_read_trylock, do_raw_read_lock);
}
@@ -200,8 +199,7 @@ static inline void __raw_write_lock_irq(rwlock_t *lock)

static inline void __raw_write_lock_bh(rwlock_t *lock)
{
- local_bh_disable();
- preempt_disable();
+ __local_bh_disable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
rwlock_acquire(&lock->dep_map, 0, 0, _RET_IP_);
LOCK_CONTENDED(lock, do_raw_write_trylock, do_raw_write_lock);
}
@@ -250,8 +248,7 @@ static inline void __raw_read_unlock_bh(rwlock_t *lock)
{
rwlock_release(&lock->dep_map, 1, _RET_IP_);
do_raw_read_unlock(lock);
- preempt_enable_no_resched();
- local_bh_enable_ip((unsigned long)__builtin_return_address(0));
+ __local_bh_enable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
}

static inline void __raw_write_unlock_irqrestore(rwlock_t *lock,
@@ -275,8 +272,7 @@ static inline void __raw_write_unlock_bh(rwlock_t *lock)
{
rwlock_release(&lock->dep_map, 1, _RET_IP_);
do_raw_write_unlock(lock);
- preempt_enable_no_resched();
- local_bh_enable_ip((unsigned long)__builtin_return_address(0));
+ __local_bh_enable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
}

#endif /* __LINUX_RWLOCK_API_SMP_H */
diff --git a/include/linux/spinlock_api_smp.h b/include/linux/spinlock_api_smp.h
index bdb9993..42dfab8 100644
--- a/include/linux/spinlock_api_smp.h
+++ b/include/linux/spinlock_api_smp.h
@@ -131,8 +131,7 @@ static inline void __raw_spin_lock_irq(raw_spinlock_t *lock)

static inline void __raw_spin_lock_bh(raw_spinlock_t *lock)
{
- local_bh_disable();
- preempt_disable();
+ __local_bh_disable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);
}
@@ -174,20 +173,17 @@ static inline void __raw_spin_unlock_bh(raw_spinlock_t *lock)
{
spin_release(&lock->dep_map, 1, _RET_IP_);
do_raw_spin_unlock(lock);
- preempt_enable_no_resched();
- local_bh_enable_ip((unsigned long)__builtin_return_address(0));
+ __local_bh_enable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
}

static inline int __raw_spin_trylock_bh(raw_spinlock_t *lock)
{
- local_bh_disable();
- preempt_disable();
+ __local_bh_disable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
if (do_raw_spin_trylock(lock)) {
spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
return 1;
}
- preempt_enable_no_resched();
- local_bh_enable_ip((unsigned long)__builtin_return_address(0));
+ __local_bh_enable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
return 0;
}

diff --git a/include/linux/spinlock_api_up.h b/include/linux/spinlock_api_up.h
index af1f472..d0d1888 100644
--- a/include/linux/spinlock_api_up.h
+++ b/include/linux/spinlock_api_up.h
@@ -24,11 +24,14 @@
* flags straight, to suppress compiler warnings of unused lock
* variables, and to add the proper checker annotations:
*/
+#define ___LOCK(lock) \
+ do { __acquire(lock); (void)(lock); } while (0)
+
#define __LOCK(lock) \
- do { preempt_disable(); __acquire(lock); (void)(lock); } while (0)
+ do { preempt_disable(); ___LOCK(lock); } while (0)

#define __LOCK_BH(lock) \
- do { local_bh_disable(); __LOCK(lock); } while (0)
+ do { __local_bh_disable_ip(_THIS_IP_, SOFTIRQ_LOCK_OFFSET); ___LOCK(lock); } while (0)

#define __LOCK_IRQ(lock) \
do { local_irq_disable(); __LOCK(lock); } while (0)
@@ -36,12 +39,15 @@
#define __LOCK_IRQSAVE(lock, flags) \
do { local_irq_save(flags); __LOCK(lock); } while (0)

+#define ___UNLOCK(lock) \
+ do { __release(lock); (void)(lock); } while (0)
+
#define __UNLOCK(lock) \
- do { preempt_enable(); __release(lock); (void)(lock); } while (0)
+ do { preempt_enable(); ___UNLOCK(lock); } while (0)

#define __UNLOCK_BH(lock) \
- do { preempt_enable_no_resched(); local_bh_enable(); \
- __release(lock); (void)(lock); } while (0)
+ do { __local_bh_enable_ip(_THIS_IP_, SOFTIRQ_LOCK_OFFSET); \
+ ___UNLOCK(lock); } while (0)

#define __UNLOCK_IRQ(lock) \
do { local_irq_enable(); __UNLOCK(lock); } while (0)
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 11025cc..7500cce1 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -107,7 +107,7 @@ static void __local_bh_disable(unsigned long ip, unsigned int cnt)
/*
* Were softirqs turned off above:
*/
- if (softirq_count() == cnt)
+ if (softirq_count() == (cnt & SOFTIRQ_MASK))
trace_softirqs_off(ip);
raw_local_irq_restore(flags);

@@ -133,7 +133,7 @@ static void __local_bh_enable(unsigned int cnt)
{
WARN_ON_ONCE(!irqs_disabled());

- if (softirq_count() == cnt)
+ if (softirq_count() == (cnt & SOFTIRQ_MASK))
trace_softirqs_on(_RET_IP_);
preempt_count_sub(cnt);

[tip-bot for Peter Zijlstra]

Commit-ID: 1774e9f3e5c8b38de3b3bc8bd0eacd280f655baf
Gitweb: http://git.kernel.org/tip/1774e9f3e5c8b38de3b3bc8bd0eacd280f655baf

Author: Peter Zijlstra <pet...@infradead.org>
AuthorDate: Tue, 19 Nov 2013 16:13:38 +0100
Committer: Ingo Molnar <mi...@kernel.org>

CommitDate: Mon, 13 Jan 2014 17:39:04 +0100

sched, net: Clean up preempt_enable_no_resched() abuse

The only valid use of preempt_enable_no_resched() is if the very next
line is schedule() or if we know preemption cannot actually be enabled
by that statement due to known more preempt_count 'refs'.

Reviewed-by: Thomas Gleixner <tg...@linutronix.de>
Signed-off-by: Peter Zijlstra <pet...@infradead.org>

Cc: r...@rjwysocki.net
Cc: Eliezer Tamir <elieze...@linux.intel.com>
Cc: David S. Miller <da...@davemloft.net>
Cc: rui....@intel.com

Cc: jacob....@linux.intel.com
Cc: Mike Galbraith <bitb...@online.de>
Cc: h...@zytor.com
Cc: Arjan van de Ven <ar...@linux.intel.com>
Cc: le...@kernel.org

Cc: Linus Torvalds <torv...@linux-foundation.org>
Cc: Andrew Morton <ak...@linux-foundation.org>
Link: http://lkml.kernel.org/r/2013111915...@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---

net/ipv4/tcp.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c4638e6..82de786 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1623,11 +1623,11 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
(len > sysctl_tcp_dma_copybreak) && !(flags & MSG_PEEK) &&
!sysctl_tcp_low_latency &&
net_dma_find_channel()) {
- preempt_enable_no_resched();
+ preempt_enable();
tp->ucopy.pinned_list =
dma_pin_iovec_pages(msg->msg_iov, len);
} else {
- preempt_enable_no_resched();
+ preempt_enable();
}
}
#endif

[tip-bot for Peter Zijlstra]

Commit-ID: 0bd3a173d711857fc9f583eb5825386cc08f3948
Gitweb: http://git.kernel.org/tip/0bd3a173d711857fc9f583eb5825386cc08f3948

Author: Peter Zijlstra <pet...@infradead.org>
AuthorDate: Tue, 19 Nov 2013 16:13:38 +0100
Committer: Ingo Molnar <mi...@kernel.org>

CommitDate: Mon, 13 Jan 2014 17:32:27 +0100

sched/preempt, locking: Rework local_bh_{dis,en}able()

Currently local_bh_disable() is out-of-line for no apparent reason.
So inline it to save a few cycles on call/return nonsense, the
function body is a single add on x86 (a few loads and store extra on
load/store archs).

Also expose two new local_bh functions:

__local_bh_{dis,en}able_ip(unsigned long ip, unsigned int cnt);

Which implement the actual local_bh_{dis,en}able() behaviour.

The next patch uses the exposed @cnt argument to optimize bh lock
functions.

With build fixes from Jacob Pan.

Cc: r...@rjwysocki.net

Cc: rui....@intel.com
Cc: jacob....@linux.intel.com
Cc: Mike Galbraith <bitb...@online.de>
Cc: h...@zytor.com
Cc: Arjan van de Ven <ar...@linux.intel.com>
Cc: le...@kernel.org

Reviewed-by: Thomas Gleixner <tg...@linutronix.de>
Signed-off-by: Peter Zijlstra <pet...@infradead.org>

Link: http://lkml.kernel.org/r/2013111915...@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---

diff --git a/include/linux/preempt_mask.h b/include/linux/preempt_mask.h
index b8d96bc..dbeec4d 100644
--- a/include/linux/preempt_mask.h
+++ b/include/linux/preempt_mask.h

@@ -2,7 +2,6 @@
#define LINUX_PREEMPT_MASK_H

#include <linux/preempt.h>
-#include <asm/hardirq.h>

/*
* We put the hardirq and softirq counter into the preemption

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 7500cce1..9e368ef 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c

static void __local_bh_enable(unsigned int cnt)
{
WARN_ON_ONCE(!irqs_disabled());

@@ -230,7 +207,7 @@ asmlinkage void __do_softirq(void)

pending = local_softirq_pending();
account_irq_enter_time(current);

- __local_bh_disable(_RET_IP_, SOFTIRQ_OFFSET);
+ __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);

lockdep_softirq_enter();

cpu = smp_processor_id();

[tip-bot for Peter Zijlstra]

Commit-ID: 37089834528be3ef8cbf927e47c753b3e272a856
Gitweb: http://git.kernel.org/tip/37089834528be3ef8cbf927e47c753b3e272a856

Author: Peter Zijlstra <pet...@infradead.org>
AuthorDate: Tue, 19 Nov 2013 16:13:38 +0100
Committer: Ingo Molnar <mi...@kernel.org>

CommitDate: Mon, 13 Jan 2014 17:39:11 +0100

sched, net: Fixup busy_loop_us_clock()

The only valid use of preempt_enable_no_resched() is if the very next
line is schedule() or if we know preemption cannot actually be enabled
by that statement due to known more preempt_count 'refs'.

This busy_poll stuff looks to be completely and utterly broken,
sched_clock() can return utter garbage with interrupts enabled (rare
but still) and it can drift unbounded between CPUs.

This means that if you get preempted/migrated and your new CPU is
years behind on the previous CPU we get to busy spin for a _very_ long
time.

There is a _REASON_ sched_clock() warns about preemptability -
papering over it with a preempt_disable()/preempt_enable_no_resched()
is just terminal brain damage on so many levels.

Replace sched_clock() usage with local_clock() which has a bounded
drift between CPUs (<2 jiffies).

There is a further problem with the entire busy wait poll thing in
that the spin time is additive to the syscall timeout, not inclusive.

Reviewed-by: Thomas Gleixner <tg...@linutronix.de>
Signed-off-by: Peter Zijlstra <pet...@infradead.org>

Cc: David S. Miller <da...@davemloft.net>

Cc: rui....@intel.com
Cc: jacob....@linux.intel.com
Cc: Mike Galbraith <bitb...@online.de>
Cc: h...@zytor.com
Cc: Arjan van de Ven <ar...@linux.intel.com>
Cc: le...@kernel.org

Cc: r...@rjwysocki.net
Cc: Eliezer Tamir <elieze...@linux.intel.com>

Cc: Linus Torvalds <torv...@linux-foundation.org>
Cc: Andrew Morton <ak...@linux-foundation.org>

Link: http://lkml.kernel.org/r/2013111915...@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---

include/net/busy_poll.h | 19 +------------------
1 file changed, 1 insertion(+), 18 deletions(-)

diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
index 829627d..1d67fb6 100644
--- a/include/net/busy_poll.h
+++ b/include/net/busy_poll.h
@@ -42,27 +42,10 @@ static inline bool net_busy_loop_on(void)

return sysctl_net_busy_poll;
}

-/* a wrapper to make debug_smp_processor_id() happy
- * we can use sched_clock() because we don't care much about precision
- * we only care that the average is bounded
- */
-#ifdef CONFIG_DEBUG_PREEMPT

-static inline u64 busy_loop_us_clock(void)
-{

- u64 rc;
-
- preempt_disable_notrace();

- rc = sched_clock();
- preempt_enable_no_resched_notrace();

-
- return rc >> 10;
-}
-#else /* CONFIG_DEBUG_PREEMPT */
static inline u64 busy_loop_us_clock(void)
{
- return sched_clock() >> 10;
+ return local_clock() >> 10;
}