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author | Peter Zijlstra <peterz@infradead.org> | 2016-05-26 10:35:03 +0200 |
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committer | Ingo Molnar <mingo@kernel.org> | 2016-06-14 11:55:15 +0200 |
commit | 726328d92a42b6d4b76078e2659f43067f82c4e8 (patch) | |
tree | 6df3622839432fc698c4404cbb0a0922a1357251 /arch/tile/lib | |
parent | b464d1270a8016edcf1fd20d77cefdecf9b0b73e (diff) | |
download | linux-stable-726328d92a42b6d4b76078e2659f43067f82c4e8.tar.gz linux-stable-726328d92a42b6d4b76078e2659f43067f82c4e8.tar.bz2 linux-stable-726328d92a42b6d4b76078e2659f43067f82c4e8.zip |
locking/spinlock, arch: Update and fix spin_unlock_wait() implementations
This patch updates/fixes all spin_unlock_wait() implementations.
The update is in semantics; where it previously was only a control
dependency, we now upgrade to a full load-acquire to match the
store-release from the spin_unlock() we waited on. This ensures that
when spin_unlock_wait() returns, we're guaranteed to observe the full
critical section we waited on.
This fixes a number of spin_unlock_wait() users that (not
unreasonably) rely on this.
I also fixed a number of ticket lock versions to only wait on the
current lock holder, instead of for a full unlock, as this is
sufficient.
Furthermore; again for ticket locks; I added an smp_rmb() in between
the initial ticket load and the spin loop testing the current value
because I could not convince myself the address dependency is
sufficient, esp. if the loads are of different sizes.
I'm more than happy to remove this smp_rmb() again if people are
certain the address dependency does indeed work as expected.
Note: PPC32 will be fixed independently
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: chris@zankel.net
Cc: cmetcalf@mellanox.com
Cc: davem@davemloft.net
Cc: dhowells@redhat.com
Cc: james.hogan@imgtec.com
Cc: jejb@parisc-linux.org
Cc: linux@armlinux.org.uk
Cc: mpe@ellerman.id.au
Cc: ralf@linux-mips.org
Cc: realmz6@gmail.com
Cc: rkuo@codeaurora.org
Cc: rth@twiddle.net
Cc: schwidefsky@de.ibm.com
Cc: tony.luck@intel.com
Cc: vgupta@synopsys.com
Cc: ysato@users.sourceforge.jp
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/tile/lib')
-rw-r--r-- | arch/tile/lib/spinlock_32.c | 6 | ||||
-rw-r--r-- | arch/tile/lib/spinlock_64.c | 6 |
2 files changed, 12 insertions, 0 deletions
diff --git a/arch/tile/lib/spinlock_32.c b/arch/tile/lib/spinlock_32.c index 88c2a53362e7..076c6cc43113 100644 --- a/arch/tile/lib/spinlock_32.c +++ b/arch/tile/lib/spinlock_32.c @@ -76,6 +76,12 @@ void arch_spin_unlock_wait(arch_spinlock_t *lock) do { delay_backoff(iterations++); } while (READ_ONCE(lock->current_ticket) == curr); + + /* + * The TILE architecture doesn't do read speculation; therefore + * a control dependency guarantees a LOAD->{LOAD,STORE} order. + */ + barrier(); } EXPORT_SYMBOL(arch_spin_unlock_wait); diff --git a/arch/tile/lib/spinlock_64.c b/arch/tile/lib/spinlock_64.c index c8d1f94ff1fe..a4b5b2cbce93 100644 --- a/arch/tile/lib/spinlock_64.c +++ b/arch/tile/lib/spinlock_64.c @@ -76,6 +76,12 @@ void arch_spin_unlock_wait(arch_spinlock_t *lock) do { delay_backoff(iterations++); } while (arch_spin_current(READ_ONCE(lock->lock)) == curr); + + /* + * The TILE architecture doesn't do read speculation; therefore + * a control dependency guarantees a LOAD->{LOAD,STORE} order. + */ + barrier(); } EXPORT_SYMBOL(arch_spin_unlock_wait); |