Commit-ID: 1f8a7633094b7886c0677b78ba60b82e501f3ce6 Gitweb: http://git.kernel.org/tip/1f8a7633094b7886c0677b78ba60b82e501f3ce6 Author: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> AuthorDate: Fri, 5 Dec 2014 21:22:22 +0900 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Wed, 14 Jan 2015 13:34:15 +0100
sched/debug: Fix potential call to __ffs(0) in sched_show_task() "struct task_struct"->state is "volatile long" and __ffs() warns that "Undefined if no bit exists, so code should check against 0 first." Therefore, at expression state = p->state ? __ffs(p->state) + 1 : 0; in sched_show_task(), CPU might see "p->state" before "?" as "non-zero" but "p->state" after "?" as "zero", which could result in "state >= sizeof(stat_nam)" being true and bogus '?' is printed. This patch changes "state" from "unsigned int" to "unsigned long" and save "p->state" before calling __ffs(), in order to avoid potential call to __ffs(0). Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Link: http://lkml.kernel.org/r/201412052131.gce35924.fvhfotlojom...@i-love.sakura.ne.jp Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/sched/core.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 56c9b79..816c172 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4508,9 +4508,10 @@ void sched_show_task(struct task_struct *p) { unsigned long free = 0; int ppid; - unsigned state; + unsigned long state = p->state; - state = p->state ? __ffs(p->state) + 1 : 0; + if (state) + state = __ffs(state) + 1; printk(KERN_INFO "%-15.15s %c", p->comm, state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?'); #if BITS_PER_LONG == 32 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
