diff options
| author | Peter Zijlstra | 2016-05-26 10:35:03 +0200 |
|---|---|---|
| committer | Ingo Molnar | 2016-06-14 11:55:15 +0200 |
| commit | 726328d92a42b6d4b76078e2659f43067f82c4e8 (patch) | |
| tree | 6df3622839432fc698c4404cbb0a0922a1357251 /arch/alpha | |
| parent | b464d1270a8016edcf1fd20d77cefdecf9b0b73e (diff) | |
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/alpha')
| -rw-r--r-- | arch/alpha/include/asm/spinlock.h | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/arch/alpha/include/asm/spinlock.h b/arch/alpha/include/asm/spinlock.h index fed9c6f44c19..a40b9fc0c6c3 100644 --- a/arch/alpha/include/asm/spinlock.h +++ b/arch/alpha/include/asm/spinlock.h @@ -3,6 +3,8 @@ #include <linux/kernel.h> #include <asm/current.h> +#include <asm/barrier.h> +#include <asm/processor.h> /* * Simple spin lock operations. There are two variants, one clears IRQ's @@ -13,8 +15,11 @@ #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock) #define arch_spin_is_locked(x) ((x)->lock != 0) -#define arch_spin_unlock_wait(x) \ - do { cpu_relax(); } while ((x)->lock) + +static inline void arch_spin_unlock_wait(arch_spinlock_t *lock) +{ + smp_cond_load_acquire(&lock->lock, !VAL); +} static inline int arch_spin_value_unlocked(arch_spinlock_t lock) { |