Re: [RFC] block: change to use atomic_inc_return_release()
> On Nov 17, 2015, at 11:38, Jens Axboe wrote: > > On 11/16/2015 08:24 PM, yalin wang wrote: >> Some arch define this atomic_inc_return_release() OP. > > That is a very vague commit message, you'll need a whole lot more than > that... A commit message is supposed to describe the reason for the change. > You provide no reason for the change. > >> diff --git a/block/bio.c b/block/bio.c >> index fbc558b..b251857 100644 >> --- a/block/bio.c >> +++ b/block/bio.c >> @@ -310,8 +310,7 @@ static void bio_chain_endio(struct bio *bio, int error) >> static inline void bio_inc_remaining(struct bio *bio) >> { >> bio->bi_flags |= (1 << BIO_CHAIN); >> -smp_mb__before_atomic(); >> -atomic_inc(&bio->__bi_remaining); >> +atomic_inc_return_release(&bio->__bi_remaining); > > Are these equivalent? Where's the documentation for this primitive? The > previous code ensured that we ordered the dec of the remaining count with the > update of the flags. > i just have a look at ARM64 implementation for this new atomic OP , but i don’t find doc in memory-barrier.txt . so i make this RFC for some response, atomic_inc_return_release() should have store_release() class memory barriers . in this example, smp_store_release() memory barrier is not enough ? just make sure bi_flags update can been seen by other cores before update atomic counter. atomic_inc_return_{release,acquire,relax} OP seems newly add to kernel . But i don’t see much users in code . Can it be used to replace lots of smp_mb__before_atomic() ? Thanks -- 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/
Re: [RFC] block: change to use atomic_inc_return_release()
On 11/16/2015 08:24 PM, yalin wang wrote: Some arch define this atomic_inc_return_release() OP. That is a very vague commit message, you'll need a whole lot more than that... A commit message is supposed to describe the reason for the change. You provide no reason for the change. diff --git a/block/bio.c b/block/bio.c index fbc558b..b251857 100644 --- a/block/bio.c +++ b/block/bio.c @@ -310,8 +310,7 @@ static void bio_chain_endio(struct bio *bio, int error) static inline void bio_inc_remaining(struct bio *bio) { bio->bi_flags |= (1 << BIO_CHAIN); - smp_mb__before_atomic(); - atomic_inc(&bio->__bi_remaining); + atomic_inc_return_release(&bio->__bi_remaining); Are these equivalent? Where's the documentation for this primitive? The previous code ensured that we ordered the dec of the remaining count with the update of the flags. -- Jens Axboe -- 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/
[RFC] block: change to use atomic_inc_return_release()
Some arch define this atomic_inc_return_release() OP. Signed-off-by: yalin wang --- block/bio.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/block/bio.c b/block/bio.c index fbc558b..b251857 100644 --- a/block/bio.c +++ b/block/bio.c @@ -310,8 +310,7 @@ static void bio_chain_endio(struct bio *bio, int error) static inline void bio_inc_remaining(struct bio *bio) { bio->bi_flags |= (1 << BIO_CHAIN); - smp_mb__before_atomic(); - atomic_inc(&bio->__bi_remaining); + atomic_inc_return_release(&bio->__bi_remaining); } /** -- 1.9.1 -- 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/