diff options
| -rw-r--r-- | kernel/sched/membarrier.c | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c index 168479a7d61b..be0ca3306be8 100644 --- a/kernel/sched/membarrier.c +++ b/kernel/sched/membarrier.c @@ -30,6 +30,23 @@ static void ipi_mb(void *info) smp_mb(); /* IPIs should be serializing but paranoid. */ } +static void ipi_sync_core(void *info) +{ + /* + * The smp_mb() in membarrier after all the IPIs is supposed to + * ensure that memory on remote CPUs that occur before the IPI + * become visible to membarrier()'s caller -- see scenario B in + * the big comment at the top of this file. + * + * A sync_core() would provide this guarantee, but + * sync_core_before_usermode() might end up being deferred until + * after membarrier()'s smp_mb(). + */ + smp_mb(); /* IPIs should be serializing but paranoid. */ + + sync_core_before_usermode(); +} + static void ipi_sync_rq_state(void *info) { struct mm_struct *mm = (struct mm_struct *) info; @@ -134,6 +151,7 @@ static int membarrier_private_expedited(int flags) int cpu; cpumask_var_t tmpmask; struct mm_struct *mm = current->mm; + smp_call_func_t ipi_func = ipi_mb; if (flags & MEMBARRIER_FLAG_SYNC_CORE) { if (!IS_ENABLED(CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE)) @@ -141,6 +159,7 @@ static int membarrier_private_expedited(int flags) if (!(atomic_read(&mm->membarrier_state) & MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY)) return -EPERM; + ipi_func = ipi_sync_core; } else { if (!(atomic_read(&mm->membarrier_state) & MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY)) @@ -181,7 +200,7 @@ static int membarrier_private_expedited(int flags) rcu_read_unlock(); preempt_disable(); - smp_call_function_many(tmpmask, ipi_mb, NULL, 1); + smp_call_function_many(tmpmask, ipi_func, NULL, 1); preempt_enable(); free_cpumask_var(tmpmask); |