2021-07-01 14:16:19

by Jason Wang

[permalink] [raw]
Subject: [PATCH v2] sched: Use BUG_ON

The BUG_ON macro simplifies the if condition followed by BUG, so that
we can use BUG_ON instead of if condition followed by BUG.

Signed-off-by: Jason Wang <[email protected]>
---
arch/powerpc/platforms/cell/spufs/sched.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 369206489895..0f218d9e5733 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -904,8 +904,8 @@ 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 */
+ /* a kernel thread never has signals pending */
+ BUG_ON(spu_acquire(ctx));

if (ctx->state != SPU_STATE_RUNNABLE)
goto out;
--
2.32.0




2021-07-02 01:45:05

by Jeremy Kerr

[permalink] [raw]
Subject: Re: [PATCH v2] sched: Use BUG_ON

Hi Jason,

> The BUG_ON macro simplifies the if condition followed by BUG, so that
> we can use BUG_ON instead of if condition followed by BUG.

[...]

> -       if (spu_acquire(ctx))
> -               BUG();  /* a kernel thread never has signals pending */
> +       /* a kernel thread never has signals pending */
> +       BUG_ON(spu_acquire(ctx));

I'm not convinced that this is an improvement; you've combined the
acquire and the BUG into a single statement, and now it's no longer
clear what the comment applies to.

If you really wanted to use BUG_ON, something like this would be more
clear:

rc = spu_acquire(ctx);
/* a kernel thread never has signals pending */
BUG_ON(rc);

but we don't have a suitable rc variable handy, so we'd need one of
those declared too. You could avoid that with:

if (spu_acquire(ctx))
BUG_ON(1); /* a kernel thread never has signals pending */

but wait: no need for the constant there, so this would be better:

if (spu_acquire(ctx))
BUG(); /* a kernel thread never has signals pending */

wait, what are we doing again?

To me, this is a bit of shuffling code around, for no real benefit.

Regards,


Jeremy