[PATCH] timer_list: Fix Wunused-const-variable

[Nathan Huckleberry]

Clang produced the following warning when using allnoconfig

kernel/time/timer_list.c:361:36: warning: unused variable
'timer_list_sops' [-Wunused-const-variable]
static const struct seq_operations timer_list_sops = {

Code reliant on CONFIG_PROC_FS is not in ifdef guard.
Created ifdef guard around proc_fs specific code.

Cc: clang-bu...@googlegroups.com
Link: https://github.com/ClangBuiltLinux/linux/issues/534
Signed-off-by: Nathan Huckleberry <nh...@google.com>
---
kernel/time/timer_list.c | 36 +++++++++++++++++++-----------------
1 file changed, 19 insertions(+), 17 deletions(-)

diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index 98ba50dcb1b2..acb326f5f50a 100644
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -282,23 +282,6 @@ static inline void timer_list_header(struct seq_file *m, u64 now)
SEQ_printf(m, "\n");
}

-static int timer_list_show(struct seq_file *m, void *v)
-{
- struct timer_list_iter *iter = v;
-
- if (iter->cpu == -1 && !iter->second_pass)
- timer_list_header(m, iter->now);
- else if (!iter->second_pass)
- print_cpu(m, iter->cpu, iter->now);
-#ifdef CONFIG_GENERIC_CLOCKEVENTS
- else if (iter->cpu == -1 && iter->second_pass)
- timer_list_show_tickdevices_header(m);
- else
- print_tickdevice(m, tick_get_device(iter->cpu), iter->cpu);
-#endif
- return 0;
-}
-
void sysrq_timer_list_show(void)
{
u64 now = ktime_to_ns(ktime_get());
@@ -317,6 +300,24 @@ void sysrq_timer_list_show(void)
return;
}

+#ifdef CONFIG_PROC_FS
+static int timer_list_show(struct seq_file *m, void *v)
+{
+ struct timer_list_iter *iter = v;
+
+ if (iter->cpu == -1 && !iter->second_pass)
+ timer_list_header(m, iter->now);
+ else if (!iter->second_pass)
+ print_cpu(m, iter->cpu, iter->now);
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+ else if (iter->cpu == -1 && iter->second_pass)
+ timer_list_show_tickdevices_header(m);
+ else
+ print_tickdevice(m, tick_get_device(iter->cpu), iter->cpu);
+#endif
+ return 0;
+}
+
static void *move_iter(struct timer_list_iter *iter, loff_t offset)
{
for (; offset; offset--) {
@@ -376,3 +377,4 @@ static int __init init_timer_list_procfs(void)
return 0;
}
__initcall(init_timer_list_procfs);
+#endif
--
2.22.0.410.gd8fdbe21b5-goog

[Nick Desaulniers]

On Fri, Jun 14, 2019 at 11:16 AM 'Nathan Huckleberry' via Clang Built
Linux <clang-bu...@googlegroups.com> wrote:
>
> Clang produced the following warning when using allnoconfig
>
> kernel/time/timer_list.c:361:36: warning: unused variable
> 'timer_list_sops' [-Wunused-const-variable]
> static const struct seq_operations timer_list_sops = {
>
> Code reliant on CONFIG_PROC_FS is not in ifdef guard.
> Created ifdef guard around proc_fs specific code.

Specifically, it sounds like proc_create_seq_private expands to an
empty GNU C statement expression (not sure why not a `static inline`
function returning `NULL` but ok), so in that case, this object full
of function pointer, and its pointed to static functions (whose sole
references are this object) all become dead code.

>
> Cc: clang-bu...@googlegroups.com
> Link: https://github.com/ClangBuiltLinux/linux/issues/534
> Signed-off-by: Nathan Huckleberry <nh...@google.com>

Thanks for the patch, looks good! Make sure to include reported by
tags when someone else has reported an issue that you fix, in this
case:

Reported-by: kbuild test robot <l...@intel.com>
Link: https://groups.google.com/forum/#!topic/clang-built-linux/w27FQOTlb70
Reviewed-by: Nick Desaulniers <ndesau...@google.com>

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--
Thanks,
~Nick Desaulniers