diff options
| author | Peter Zijlstra (Intel) <peterz@infradead.org> | 2015-04-24 20:56:36 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-05-08 12:36:58 +0200 |
| commit | 2aa79af64263190eec610422b07f60e99a7d230a (patch) | |
| tree | 423641cd1ae46f066739d62d743f39c7eb58c5c8 | |
| parent | locking/qspinlock: Use a simple write to grab the lock (diff) | |
| download | linux-2aa79af64263190eec610422b07f60e99a7d230a.tar.xz linux-2aa79af64263190eec610422b07f60e99a7d230a.zip | |
locking/qspinlock: Revert to test-and-set on hypervisors
When we detect a hypervisor (!paravirt, see qspinlock paravirt support
patches), revert to a simple test-and-set lock to avoid the horrors
of queue preemption.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Douglas Hatch <doug.hatch@hp.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paolo Bonzini <paolo.bonzini@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1429901803-29771-8-git-send-email-Waiman.Long@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | arch/x86/include/asm/qspinlock.h | 14 | ||||
| -rw-r--r-- | include/asm-generic/qspinlock.h | 7 | ||||
| -rw-r--r-- | kernel/locking/qspinlock.c | 3 |
3 files changed, 24 insertions, 0 deletions
diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h index e2aee8273664..f079b7020e3f 100644 --- a/arch/x86/include/asm/qspinlock.h +++ b/arch/x86/include/asm/qspinlock.h @@ -1,6 +1,7 @@ #ifndef _ASM_X86_QSPINLOCK_H #define _ASM_X86_QSPINLOCK_H +#include <asm/cpufeature.h> #include <asm-generic/qspinlock_types.h> #define queued_spin_unlock queued_spin_unlock @@ -15,6 +16,19 @@ static inline void queued_spin_unlock(struct qspinlock *lock) smp_store_release((u8 *)lock, 0); } +#define virt_queued_spin_lock virt_queued_spin_lock + +static inline bool virt_queued_spin_lock(struct qspinlock *lock) +{ + if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) + return false; + + while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0) + cpu_relax(); + + return true; +} + #include <asm-generic/qspinlock.h> #endif /* _ASM_X86_QSPINLOCK_H */ diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h index 569abcd47a9a..83bfb87f5bf1 100644 --- a/include/asm-generic/qspinlock.h +++ b/include/asm-generic/qspinlock.h @@ -111,6 +111,13 @@ static inline void queued_spin_unlock_wait(struct qspinlock *lock) cpu_relax(); } +#ifndef virt_queued_spin_lock +static __always_inline bool virt_queued_spin_lock(struct qspinlock *lock) +{ + return false; +} +#endif + /* * Initializier */ diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index 033872113ebb..fd31a474145d 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -249,6 +249,9 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val) BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS)); + if (virt_queued_spin_lock(lock)) + return; + /* * wait for in-progress pending->locked hand-overs * |