Messages in this thread Patch in this message | | | From | Rusty Russell <> | Subject | Re: [PATCH] Introduce down_nowait() | Date | Wed, 21 May 2008 17:56:04 +1000 |
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On Wednesday 21 May 2008 16:29:03 Andrew Morton wrote: > On Wed, 21 May 2008 16:00:15 +1000 Rusty Russell <rusty@rustcorp.com.au> wrote: > > Andrew suggested introducing "down_nowait" as a wrapper now, to make > > the transition easier. > > ... > > +/** > > + * down_nowait - try to down a semaphore, but don't block > > + * @sem: the semaphore > > + * > > Actually, I don't thing down_nowait() is a terribly good name, because it > doesn't tell the reader anything about what to expect from the return > value. Does a non-zero return mean that down_wait() acquired the lock, > or does it not? Something like down_try() would be better, because if > it returns 1 we can say "ah, the trying succeeded".'
I agree: that was my first name. Christoph hated it.
> Except "down_nowait" doesn't have "try" in its name. down_try() would > be better?
What a great name! You're a genius!
Subject: [PATCH] Introduce down_try()
I planned on removing the much-disliked down_trylock() (with its backwards return codes) in 2.6.27, but it's creating something of a logjam with other patches in -mm and linux-next.
Andrew suggested introducing "down_try" as a wrapper now, to make the transition easier.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Matthew Wilcox <matthew@wil.cx> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
diff -r 92664ae4130b include/linux/semaphore.h --- a/include/linux/semaphore.h Wed May 21 14:54:40 2008 +1000 +++ b/include/linux/semaphore.h Wed May 21 15:07:31 2008 +1000 @@ -48,4 +48,18 @@ extern int __must_check down_timeout(str extern int __must_check down_timeout(struct semaphore *sem, long jiffies); extern void up(struct semaphore *sem); +/** + * down_try - try to down a semaphore, but don't block + * @sem: the semaphore + * + * This is equivalent to down_trylock(), but has the same return codes as + * spin_trylock and mutex_trylock: 1 if semaphore acquired, 0 if not. + * + * down_trylock() with its confusing return codes will be deprecated + * soon. It will not be missed. + */ +static inline int __must_check down_try(struct semaphore *sem) +{ + return !down_trylock(sem); +} #endif /* __LINUX_SEMAPHORE_H */
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