[PATCH] x86, Fix do_IRQ interrupt warning for cpu hotplug retriggered irqs [v3]

[Prarit Bhargava]

I tested this by doing a continuous loop of booting a system, downing all
cpus, and then rebooting. Before every reboot I grepped the dmesg log for
the do_IRQ warning to see if there were any additional do_IRQ warnings and
I do not see any after applying this patch. I also tested on several
small and medium sized boxes to confirm that cpu hotplug still works there
too and do not see any issues. Please note that this patchset was tested
in conjunction with

http://marc.info/?l=linux-edac&m=138783131400902&w=2

and

http://marc.info/?l=linux-kernel&m=138871006718478&w=2

in order to get cpu hotplug working.

I'm redoing some additional stability testing (with the additional 2 line
change in this version of the patch) after down'ing all cpus and
bringing them back into service, however, I don't expect to see any new issues.

P.

----8<----

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=64831

When downing a cpu it is possible that there are unhandled irqs left in
the APIC IRR register. The following code path shows how the problem
can occur:

1. CPU 5 is to go down.
2. cpu_disable() on CPU 5 executes with interrupt flag cleared by
local_irq_save() via stop_machine().
3. IRQ 12 asserts on CPU 5, setting IRR but not ISR because interrupt
flag is cleared (CPU unabled to handle the irq)
4. IRQs are migrated off of CPU 5, and the vectors' irqs are set to -1.
5. stop_machine() finishes cpu_disable()
6. cpu_die() for CPU 5 executes in normal context.
7. CPU 5 attempts to handle IRQ 12 because the IRR is set for IRQ 12. The
code attempts to find the vector's IRQ and cannot because it has been set to -1.
8. do_IRQ warning displays warning about CPU 5 IRQ 12.

When this happens, do_IRQ() spits out a warning like

kernel: [ 614.414443] do_IRQ: 5.124 No irq handler for vector (irq -1)

I added a debug printk to output which CPU & vector was retriggered and
discovered that that we are getting bogus events. I see a 100% correlation
between this debug printk in fixup_irqs() and the do_IRQ() warning.

This patchset resolves this by adding definitions for VECTOR_UNDEFINED(-1) and
VECTOR_RETRIGGERED(-2) and modifying the code to use them.

[v2]: sent with more detailed commit message
[v3]: set vector_irq[irq] back to VECTOR_UNDEFINED after call in do_IRQ()

Signed-off-by: Prarit Bhargava <pra...@redhat.com>
Cc: Thomas Gleixner <tg...@linutronix.de>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: x...@kernel.org
Cc: Michel Lespinasse <wal...@google.com>
Cc: Andi Kleen <a...@linux.intel.com>
Cc: Seiji Aguchi <seiji....@hds.com>
Cc: Yang Zhang <yang.z...@Intel.com>
Cc: Paul Gortmaker <paul.go...@windriver.com>
Cc: janet....@intel.com
Cc: tony...@intel.com
Cc: ruiv...@gmail.com
---
arch/x86/include/asm/hw_irq.h | 2 ++
arch/x86/kernel/apic/io_apic.c | 13 +++++++------
arch/x86/kernel/irq.c | 20 ++++++++++++++------
arch/x86/kernel/irqinit.c | 4 ++--
4 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index 92b3bae..22c425e 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -188,6 +188,8 @@ extern __visible void smp_invalidate_interrupt(struct pt_regs *);

extern void (*__initconst interrupt[NR_VECTORS-FIRST_EXTERNAL_VECTOR])(void);

+#define VECTOR_UNDEFINED -1
+#define VECTOR_RETRIGGERED -2
typedef int vector_irq_t[NR_VECTORS];
DECLARE_PER_CPU(vector_irq_t, vector_irq);
extern void setup_vector_irq(int cpu);
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index e63a5bd..6e1541c 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1143,7 +1143,8 @@ next:
goto next;

for_each_cpu_and(new_cpu, tmp_mask, cpu_online_mask)
- if (per_cpu(vector_irq, new_cpu)[vector] != -1)
+ if (per_cpu(vector_irq, new_cpu)[vector] >
+ VECTOR_UNDEFINED)
goto next;
/* Found one! */
current_vector = vector;
@@ -1183,7 +1184,7 @@ static void __clear_irq_vector(int irq, struct irq_cfg *cfg)

vector = cfg->vector;
for_each_cpu_and(cpu, cfg->domain, cpu_online_mask)
- per_cpu(vector_irq, cpu)[vector] = -1;
+ per_cpu(vector_irq, cpu)[vector] = VECTOR_UNDEFINED;

cfg->vector = 0;
cpumask_clear(cfg->domain);
@@ -1195,7 +1196,7 @@ static void __clear_irq_vector(int irq, struct irq_cfg *cfg)
vector++) {
if (per_cpu(vector_irq, cpu)[vector] != irq)
continue;
- per_cpu(vector_irq, cpu)[vector] = -1;
+ per_cpu(vector_irq, cpu)[vector] = VECTOR_UNDEFINED;
break;
}
}
@@ -1228,12 +1229,12 @@ void __setup_vector_irq(int cpu)
/* Mark the free vectors */
for (vector = 0; vector < NR_VECTORS; ++vector) {
irq = per_cpu(vector_irq, cpu)[vector];
- if (irq < 0)
+ if (irq <= VECTOR_UNDEFINED)
continue;

cfg = irq_cfg(irq);
if (!cpumask_test_cpu(cpu, cfg->domain))
- per_cpu(vector_irq, cpu)[vector] = -1;
+ per_cpu(vector_irq, cpu)[vector] = VECTOR_UNDEFINED;
}
raw_spin_unlock(&vector_lock);
}
@@ -2208,7 +2209,7 @@ asmlinkage void smp_irq_move_cleanup_interrupt(void)
struct irq_cfg *cfg;
irq = __this_cpu_read(vector_irq[vector]);

- if (irq == -1)
+ if (irq <= VECTOR_UNDEFINED)
continue;

desc = irq_to_desc(irq);
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 22d0687..8e9f0aa 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -193,9 +193,13 @@ __visible unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
if (!handle_irq(irq, regs)) {
ack_APIC_irq();

- if (printk_ratelimit())
- pr_emerg("%s: %d.%d No irq handler for vector (irq %d)\n",
- __func__, smp_processor_id(), vector, irq);
+ if (irq != VECTOR_RETRIGGERED)
+ pr_emerg_ratelimited("%s: %d.%d No irq handler for vector (irq %d)\n",
+ __func__, smp_processor_id(),
+ vector, irq);
+ else
+ __this_cpu_write(vector_irq[vector],
+ VECTOR_UNDEFINED);
}

irq_exit();
@@ -344,7 +348,7 @@ void fixup_irqs(void)
for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) {
unsigned int irr;

- if (__this_cpu_read(vector_irq[vector]) < 0)
+ if (__this_cpu_read(vector_irq[vector]) <= VECTOR_UNDEFINED)
continue;

irr = apic_read(APIC_IRR + (vector / 32 * 0x10));
@@ -355,11 +359,15 @@ void fixup_irqs(void)
data = irq_desc_get_irq_data(desc);
chip = irq_data_get_irq_chip(data);
raw_spin_lock(&desc->lock);
- if (chip->irq_retrigger)
+ if (chip->irq_retrigger) {
chip->irq_retrigger(data);
+ __this_cpu_write(vector_irq[vector],
+ VECTOR_RETRIGGERED);
+ }
raw_spin_unlock(&desc->lock);
}
- __this_cpu_write(vector_irq[vector], -1);
+ if (__this_cpu_read(vector_irq[vector]) != VECTOR_RETRIGGERED)
+ __this_cpu_write(vector_irq[vector], VECTOR_UNDEFINED);
}
}
#endif
diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
index a2a1fbc..7f50156 100644
--- a/arch/x86/kernel/irqinit.c
+++ b/arch/x86/kernel/irqinit.c
@@ -52,7 +52,7 @@ static struct irqaction irq2 = {
};

DEFINE_PER_CPU(vector_irq_t, vector_irq) = {
- [0 ... NR_VECTORS - 1] = -1,
+ [0 ... NR_VECTORS - 1] = VECTOR_UNDEFINED,
};

int vector_used_by_percpu_irq(unsigned int vector)
@@ -60,7 +60,7 @@ int vector_used_by_percpu_irq(unsigned int vector)
int cpu;

for_each_online_cpu(cpu) {
- if (per_cpu(vector_irq, cpu)[vector] != -1)
+ if (per_cpu(vector_irq, cpu)[vector] > VECTOR_UNDEFINED)
return 1;
}

--
1.7.9.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majo...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

[rui wang]

If it precisely catches the remaining IRR, then it is something good to have.

Reviewed-by: Rui Wang <rui.y...@intel.com>

Thanks
Rui

[tip-bot for Prarit Bhargava]

Commit-ID: 9345005f4eed805308193658d12e4e7e9c261e74
Gitweb: http://git.kernel.org/tip/9345005f4eed805308193658d12e4e7e9c261e74
Author: Prarit Bhargava <pra...@redhat.com>
AuthorDate: Sun, 5 Jan 2014 11:10:52 -0500
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Sun, 12 Jan 2014 13:13:02 +0100

x86/irq: Fix do_IRQ() interrupt warning for cpu hotplug retriggered irqs

During heavy CPU-hotplug operations the following spurious kernel warnings
can trigger:

do_IRQ: No ... irq handler for vector (irq -1)

[ See: https://bugzilla.kernel.org/show_bug.cgi?id=64831 ]

When downing a cpu it is possible that there are unhandled irqs
left in the APIC IRR register. The following code path shows
how the problem can occur:

1. CPU 5 is to go down.

2. cpu_disable() on CPU 5 executes with interrupt flag cleared
by local_irq_save() via stop_machine().

3. IRQ 12 asserts on CPU 5, setting IRR but not ISR because
interrupt flag is cleared (CPU unabled to handle the irq)

4. IRQs are migrated off of CPU 5, and the vectors' irqs are set
to -1. 5. stop_machine() finishes cpu_disable()

6. cpu_die() for CPU 5 executes in normal context.

7. CPU 5 attempts to handle IRQ 12 because the IRR is set for
IRQ 12. The code attempts to find the vector's IRQ and cannot

because it has been set to -1. 8. do_IRQ() warning displays

warning about CPU 5 IRQ 12.

I added a debug printk to output which CPU & vector was
retriggered and discovered that that we are getting bogus
events. I see a 100% correlation between this debug printk in
fixup_irqs() and the do_IRQ() warning.

This patchset resolves this by adding definitions for
VECTOR_UNDEFINED(-1) and VECTOR_RETRIGGERED(-2) and modifying
the code to use them.

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=64831
Signed-off-by: Prarit Bhargava <pra...@redhat.com>
Reviewed-by: Rui Wang <rui.y...@intel.com>
Cc: Michel Lespinasse <wal...@google.com>

Cc: Seiji Aguchi <seiji....@hds.com>
Cc: Yang Zhang <yang.z...@Intel.com>
Cc: Paul Gortmaker <paul.go...@windriver.com>

Cc: janet....@Intel.com
Cc: tony...@Intel.com
Cc: ruiv...@gmail.com
Link: http://lkml.kernel.org/r/1388938252-16627-1-g...@redhat.com
[ Cleaned up the code a bit. ]
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
arch/x86/include/asm/hw_irq.h | 3 +++
arch/x86/kernel/apic/io_apic.c | 18 +++++++++---------
arch/x86/kernel/irq.c | 19 +++++++++++++------
arch/x86/kernel/irqinit.c | 4 ++--
4 files changed, 27 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index cba45d9..67d69b8 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -191,6 +191,9 @@ extern void (*__initconst interrupt[NR_VECTORS-FIRST_EXTERNAL_VECTOR])(void);
#define trace_interrupt interrupt
#endif

+#define VECTOR_UNDEFINED -1
+#define VECTOR_RETRIGGERED -2

+

typedef int vector_irq_t[NR_VECTORS];
DECLARE_PER_CPU(vector_irq_t, vector_irq);
extern void setup_vector_irq(int cpu);
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c

index e63a5bd..6df0b66 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1142,9 +1142,10 @@ next:
if (test_bit(vector, used_vectors))
goto next;

- for_each_cpu_and(new_cpu, tmp_mask, cpu_online_mask)

- if (per_cpu(vector_irq, new_cpu)[vector] != -1)

+ for_each_cpu_and(new_cpu, tmp_mask, cpu_online_mask) {
+ if (per_cpu(vector_irq, new_cpu)[vector] > VECTOR_UNDEFINED)
goto next;
+ }

/* Found one! */
current_vector = vector;

current_offset = offset;

@@ -1183,7 +1184,7 @@ static void __clear_irq_vector(int irq, struct irq_cfg *cfg)

vector = cfg->vector;
for_each_cpu_and(cpu, cfg->domain, cpu_online_mask)
- per_cpu(vector_irq, cpu)[vector] = -1;
+ per_cpu(vector_irq, cpu)[vector] = VECTOR_UNDEFINED;

cfg->vector = 0;
cpumask_clear(cfg->domain);

@@ -1191,11 +1192,10 @@ static void __clear_irq_vector(int irq, struct irq_cfg *cfg)
if (likely(!cfg->move_in_progress))
return;
for_each_cpu_and(cpu, cfg->old_domain, cpu_online_mask) {
- for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS;
- vector++) {
+ for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) {

if (per_cpu(vector_irq, cpu)[vector] != irq)
continue;
- per_cpu(vector_irq, cpu)[vector] = -1;
+ per_cpu(vector_irq, cpu)[vector] = VECTOR_UNDEFINED;
break;
}
}

@@ -1228,12 +1228,12 @@ void __setup_vector_irq(int cpu)

/* Mark the free vectors */
for (vector = 0; vector < NR_VECTORS; ++vector) {
irq = per_cpu(vector_irq, cpu)[vector];
- if (irq < 0)
+ if (irq <= VECTOR_UNDEFINED)
continue;

cfg = irq_cfg(irq);
if (!cpumask_test_cpu(cpu, cfg->domain))
- per_cpu(vector_irq, cpu)[vector] = -1;
+ per_cpu(vector_irq, cpu)[vector] = VECTOR_UNDEFINED;
}
raw_spin_unlock(&vector_lock);
}

@@ -2208,7 +2208,7 @@ asmlinkage void smp_irq_move_cleanup_interrupt(void)

struct irq_cfg *cfg;
irq = __this_cpu_read(vector_irq[vector]);

- if (irq == -1)
+ if (irq <= VECTOR_UNDEFINED)
continue;

desc = irq_to_desc(irq);
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c

index 22d0687..884d875 100644

--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -193,9 +193,13 @@ __visible unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
if (!handle_irq(irq, regs)) {
ack_APIC_irq();

- if (printk_ratelimit())
- pr_emerg("%s: %d.%d No irq handler for vector (irq %d)\n",
- __func__, smp_processor_id(), vector, irq);
+ if (irq != VECTOR_RETRIGGERED) {
+ pr_emerg_ratelimited("%s: %d.%d No irq handler for vector (irq %d)\n",
+ __func__, smp_processor_id(),
+ vector, irq);
+ } else {

+ __this_cpu_write(vector_irq[vector], VECTOR_UNDEFINED);
+ }

}

irq_exit();
@@ -344,7 +348,7 @@ void fixup_irqs(void)
for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) {
unsigned int irr;

- if (__this_cpu_read(vector_irq[vector]) < 0)
+ if (__this_cpu_read(vector_irq[vector]) <= VECTOR_UNDEFINED)
continue;

irr = apic_read(APIC_IRR + (vector / 32 * 0x10));

@@ -355,11 +359,14 @@ void fixup_irqs(void)

data = irq_desc_get_irq_data(desc);
chip = irq_data_get_irq_chip(data);
raw_spin_lock(&desc->lock);
- if (chip->irq_retrigger)
+ if (chip->irq_retrigger) {
chip->irq_retrigger(data);

+ __this_cpu_write(vector_irq[vector], VECTOR_RETRIGGERED);

+ }
raw_spin_unlock(&desc->lock);
}
- __this_cpu_write(vector_irq[vector], -1);
+ if (__this_cpu_read(vector_irq[vector]) != VECTOR_RETRIGGERED)
+ __this_cpu_write(vector_irq[vector], VECTOR_UNDEFINED);
}
}
#endif
diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
index a2a1fbc..7f50156 100644
--- a/arch/x86/kernel/irqinit.c
+++ b/arch/x86/kernel/irqinit.c
@@ -52,7 +52,7 @@ static struct irqaction irq2 = {
};

DEFINE_PER_CPU(vector_irq_t, vector_irq) = {
- [0 ... NR_VECTORS - 1] = -1,
+ [0 ... NR_VECTORS - 1] = VECTOR_UNDEFINED,
};

int vector_used_by_percpu_irq(unsigned int vector)
@@ -60,7 +60,7 @@ int vector_used_by_percpu_irq(unsigned int vector)
int cpu;

for_each_online_cpu(cpu) {
- if (per_cpu(vector_irq, cpu)[vector] != -1)
+ if (per_cpu(vector_irq, cpu)[vector] > VECTOR_UNDEFINED)
return 1;
}

--