diff options
author | Andrea Parri <andrea.parri@amarulasolutions.com> | 2018-05-15 02:01:28 +0300 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2018-05-15 09:11:15 +0300 |
commit | c6f5d02b6a0fb91be5d656885ce02cf28952181d (patch) | |
tree | bc968eebe4e82871210b65cae0cfb9e82658be04 /include/linux/mutex.h | |
parent | b7e4aadef28f217de8907eec60a964328797a2be (diff) | |
download | linux-c6f5d02b6a0fb91be5d656885ce02cf28952181d.tar.xz |
locking/spinlocks/arm64: Remove smp_mb() from arch_spin_is_locked()
The following commit:
38b850a73034f ("arm64: spinlock: order spin_{is_locked,unlock_wait} against local locks")
... added an smp_mb() to arch_spin_is_locked(), in order
"to ensure that the lock value is always loaded after any other locks have
been taken by the current CPU", and reported one example (the "insane case"
in ipc/sem.c) relying on such guarantee.
It is however understood that spin_is_locked() is not required to provide
such an ordering guarantee (a guarantee that is currently not provided by
all the implementations/archs), and that callers relying on such ordering
should instead insert suitable memory barriers before acting on the result
of spin_is_locked().
Following a recent auditing [1] of the callers of {,raw_}spin_is_locked(),
revealing that none of them are relying on the ordering guarantee anymore,
this commit removes the leading smp_mb() from the primitive thus reverting
38b850a73034f.
[1] https://marc.info/?l=linux-kernel&m=151981440005264&w=2
https://marc.info/?l=linux-kernel&m=152042843808540&w=2
https://marc.info/?l=linux-kernel&m=152043346110262&w=2
Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akiyks@gmail.com
Cc: boqun.feng@gmail.com
Cc: dhowells@redhat.com
Cc: j.alglave@ucl.ac.uk
Cc: linux-arch@vger.kernel.org
Cc: luc.maranget@inria.fr
Cc: npiggin@gmail.com
Cc: parri.andrea@gmail.com
Cc: stern@rowland.harvard.edu
Link: http://lkml.kernel.org/r/1526338889-7003-2-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/mutex.h')
0 files changed, 0 insertions, 0 deletions