| Date | Wed, 15 Aug 2012 07:08:08 -0700 | From | Greg Kroah-Hartman <> | Subject | Re: [ 20/82] ARM: 7467/1: mutex: use generic xchg-based implementation for ARMv6+ |
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On Wed, Aug 15, 2012 at 02:56:22PM +0100, Ben Hutchings wrote: > On Mon, 2012-08-13 at 13:18 -0700, Greg Kroah-Hartman wrote: > > From: Greg KH <gregkh@linuxfoundation.org> > > > > 3.5-stable review patch. If anyone has any objections, please let me know. > > > > ------------------ > > > > From: Will Deacon <will.deacon@arm.com> > > > > commit a76d7bd96d65fa5119adba97e1b58d95f2e78829 upstream. > > > > The open-coded mutex implementation for ARMv6+ cores suffers from a > > severe lack of barriers, so in the uncontended case we don't actually > > protect any accesses performed during the critical section. > > > > Furthermore, the code is largely a duplication of the ARMv6+ atomic_dec > > code but optimised to remove a branch instruction, as the mutex fastpath > > was previously inlined. Now that this is executed out-of-line, we can > > reuse the atomic access code for the locking (in fact, we use the xchg > > code as this produces shorter critical sections). > > > > This patch uses the generic xchg based implementation for mutexes on > > ARMv6+, which introduces barriers to the lock/unlock operations and also > > has the benefit of removing a fair amount of inline assembly code. > [...] > > Here also, I think this should be deferred.
"also"? Am I missing some context here? Why should we deferr this one? What do we need to wait for?
confused,
greg k-h
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