rwsem: skip initial trylock in rwsem_down_write_failed
authorMichel Lespinasse <walken@google.com>
Tue, 7 May 2013 13:45:57 +0000 (06:45 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 7 May 2013 14:20:16 +0000 (07:20 -0700)
commit9b0fc9c09f1b262b7fe697eba6b05095d78850e5
tree5fb25ae32c9aed77f604858a77a27cd4b37bbfc6
parenta7d2c573ae7fad1b2c877d1a1342fa5bb0d6478c
rwsem: skip initial trylock in rwsem_down_write_failed

We can skip the initial trylock in rwsem_down_write_failed() if there
are known active lockers already, thus saving one likely-to-fail
cmpxchg.

Signed-off-by: Michel Lespinasse <walken@google.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
lib/rwsem.c