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Subject[PATCH 1/1] powerpc: get_wchan(): solve possible race scenario due to parallel wakeup
Date
Add a check for p->state == TASK_RUNNING so that any wake-ups on
task_struct p in the interim lead to 0 being returned by get_wchan().

Signed-off-by: Kautuk Consul <kautuk.consul.1980@gmail.com>
---
arch/powerpc/kernel/process.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index b8500b4..f233352 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1785,7 +1785,8 @@ unsigned long get_wchan(struct task_struct *p)

do {
sp = *(unsigned long *)sp;
- if (!validate_sp(sp, p, STACK_FRAME_OVERHEAD))
+ if (!validate_sp(sp, p, STACK_FRAME_OVERHEAD) ||
+ p->state == TASK_RUNNING)
return 0;
if (count > 0) {
ip = ((unsigned long *)sp)[STACK_FRAME_LR_SAVE];
--
1.7.9.5
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