[PATCH v2] sched: replace if (cond) BUG() with WARN_ON()

[PATCH v2] sched: replace if (cond) BUG() with WARN_ON()

[Jiapeng Chong]

Fix the following coccicheck warnings:

./arch/powerpc/platforms/cell/spufs/sched.c:908:2-5: WARNING: Use BUG_ON
instead of if condition followed by BUG.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
---
Changes in v2:
  - replace BUG with WARN_ON.

 arch/powerpc/platforms/cell/spufs/sched.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 3692064..1031448 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -904,8 +904,7 @@ static noinline void spusched_tick(struct spu_context *ctx)
 	struct spu_context *new = NULL;
 	struct spu *spu = NULL;
 
-	if (spu_acquire(ctx))
-		BUG();	/* a kernel thread never has signals pending */
+	WARN_ON(spu_acquire(ctx));	/* a kernel thread never has signals pending */
 
 	if (ctx->state != SPU_STATE_RUNNABLE)
 		goto out;
-- 
1.8.3.1

[PATCH v2] sched: replace if (cond) BUG() with WARN_ON()

[Jiapeng Chong]

Fix the following coccicheck warnings:

./arch/powerpc/platforms/cell/spufs/sched.c:908:2-5: WARNING: Use BUG_ON
instead of if condition followed by BUG.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
---
Changes in v2:
  - replace BUG with WARN_ON.

 arch/powerpc/platforms/cell/spufs/sched.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 3692064..1031448 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -904,8 +904,7 @@ static noinline void spusched_tick(struct spu_context *ctx)
 	struct spu_context *new = NULL;
 	struct spu *spu = NULL;
 
-	if (spu_acquire(ctx))
-		BUG();	/* a kernel thread never has signals pending */
+	WARN_ON(spu_acquire(ctx));	/* a kernel thread never has signals pending */
 
 	if (ctx->state != SPU_STATE_RUNNABLE)
 		goto out;
-- 
1.8.3.1

Re: [PATCH v2] sched: replace if (cond) BUG() with WARN_ON()

[Arnd Bergmann]

On Wed, Mar 17, 2021 at 8:35 AM Jiapeng Chong
<jiapeng.chong@linux.alibaba.com> wrote:
>
> Fix the following coccicheck warnings:
>
> ./arch/powerpc/platforms/cell/spufs/sched.c:908:2-5: WARNING: Use BUG_ON
> instead of if condition followed by BUG.
>
> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>

If you change it from BUG() to WARN_ON(), you should explain why it's safe to
do that in this case. Here it is not, since the following spu_release() will
end up making things worse if the acquire failed. Also if there was a signal
pending, then spusched_tick() will just get called again and constantly
print these warnings.

There is probably a way to use WARN_ON_ONCE() here, in combination
with a way to terminate the thread safely, but this has to be done carefully.

       Arnd

Re: [PATCH v2] sched: replace if (cond) BUG() with WARN_ON()

[Arnd Bergmann]

On Wed, Mar 17, 2021 at 8:35 AM Jiapeng Chong
<jiapeng.chong@linux.alibaba.com> wrote:
>
> Fix the following coccicheck warnings:
>
> ./arch/powerpc/platforms/cell/spufs/sched.c:908:2-5: WARNING: Use BUG_ON
> instead of if condition followed by BUG.
>
> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>

If you change it from BUG() to WARN_ON(), you should explain why it's safe to
do that in this case. Here it is not, since the following spu_release() will
end up making things worse if the acquire failed. Also if there was a signal
pending, then spusched_tick() will just get called again and constantly
print these warnings.

There is probably a way to use WARN_ON_ONCE() here, in combination
with a way to terminate the thread safely, but this has to be done carefully.

       Arnd