diff options
author | Peter Zijlstra <peterz@infradead.org> | 2016-05-26 08:35:03 (GMT) |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2016-06-14 09:55:15 (GMT) |
commit | 726328d92a42b6d4b76078e2659f43067f82c4e8 (patch) | |
tree | 6df3622839432fc698c4404cbb0a0922a1357251 /include | |
parent | b464d1270a8016edcf1fd20d77cefdecf9b0b73e (diff) | |
download | linux-726328d92a42b6d4b76078e2659f43067f82c4e8.tar.xz |
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 'include')
-rw-r--r-- | include/asm-generic/barrier.h | 2 | ||||
-rw-r--r-- | include/linux/spinlock_up.h | 10 |
2 files changed, 8 insertions, 4 deletions
diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h index ab7b0bd..fe297b5 100644 --- a/include/asm-generic/barrier.h +++ b/include/asm-generic/barrier.h @@ -194,7 +194,7 @@ do { \ }) #endif -#endif +#endif /* CONFIG_SMP */ /* Barriers for virtual machine guests when talking to an SMP host */ #define virt_mb() __smp_mb() diff --git a/include/linux/spinlock_up.h b/include/linux/spinlock_up.h index 8b3ac0d..0d9848d 100644 --- a/include/linux/spinlock_up.h +++ b/include/linux/spinlock_up.h @@ -6,6 +6,7 @@ #endif #include <asm/processor.h> /* for cpu_relax() */ +#include <asm/barrier.h> /* * include/linux/spinlock_up.h - UP-debug version of spinlocks. @@ -25,6 +26,11 @@ #ifdef CONFIG_DEBUG_SPINLOCK #define arch_spin_is_locked(x) ((x)->slock == 0) +static inline void arch_spin_unlock_wait(arch_spinlock_t *lock) +{ + smp_cond_load_acquire(&lock->slock, VAL); +} + static inline void arch_spin_lock(arch_spinlock_t *lock) { lock->slock = 0; @@ -67,6 +73,7 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock) #else /* DEBUG_SPINLOCK */ #define arch_spin_is_locked(lock) ((void)(lock), 0) +#define arch_spin_unlock_wait(lock) do { barrier(); (void)(lock); } while (0) /* for sched/core.c and kernel_lock.c: */ # define arch_spin_lock(lock) do { barrier(); (void)(lock); } while (0) # define arch_spin_lock_flags(lock, flags) do { barrier(); (void)(lock); } while (0) @@ -79,7 +86,4 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock) #define arch_read_can_lock(lock) (((void)(lock), 1)) #define arch_write_can_lock(lock) (((void)(lock), 1)) -#define arch_spin_unlock_wait(lock) \ - do { cpu_relax(); } while (arch_spin_is_locked(lock)) - #endif /* __LINUX_SPINLOCK_UP_H */ |