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sched/membarrier: Return -ENOMEM to userspace on memory allocation failure 

Remove the IPI fallback code from membarrier to deal with very
infrequent cpumask memory allocation failure. Use GFP_KERNEL rather
than GFP_NOWAIT, and relax the blocking guarantees for the expedited
membarrier system call commands, allowing it to block if waiting for
memory to be made available.

In addition, now -ENOMEM can be returned to user-space if the cpumask
memory allocation fails.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190919173705.2181-8-mathieu.desnoyers@efficios.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Mathieu Desnoyers 2019-09-19 13:37:05 -04:00 committed by Ingo Molnar
parent c6d68c1c4a
commit c172e0a3e8
1 changed files with 20 additions and 43 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

63
kernel/sched/membarrier.c
View File

@ -66,7 +66,6 @@ void membarrier_exec_mmap(struct mm_struct *mm)
static int membarrier_global_expedited(void)
{
int cpu;
bool fallback = false;
cpumask_var_t tmpmask;
if (num_online_cpus() == 1)
@ -78,15 +77,8 @@ static int membarrier_global_expedited(void)
*/
smp_mb(); /* system call entry is not a mb. */
/*
* Expedited membarrier commands guarantee that they won't
* block, hence the GFP_NOWAIT allocation flag and fallback
* implementation.
*/
if (!zalloc_cpumask_var(&tmpmask, GFP_NOWAIT)) {
/* Fallback for OOM. */
fallback = true;
}
if (!zalloc_cpumask_var(&tmpmask, GFP_KERNEL))
return -ENOMEM;
cpus_read_lock();
rcu_read_lock();
@ -117,18 +109,15 @@ static int membarrier_global_expedited(void)
if (p->flags & PF_KTHREAD)
continue;
if (!fallback)
__cpumask_set_cpu(cpu, tmpmask);
else
smp_call_function_single(cpu, ipi_mb, NULL, 1);
__cpumask_set_cpu(cpu, tmpmask);
}
rcu_read_unlock();
if (!fallback) {
preempt_disable();
smp_call_function_many(tmpmask, ipi_mb, NULL, 1);
preempt_enable();
free_cpumask_var(tmpmask);
}
preempt_disable();
smp_call_function_many(tmpmask, ipi_mb, NULL, 1);
preempt_enable();
free_cpumask_var(tmpmask);
cpus_read_unlock();
/*
@ -143,7 +132,6 @@ static int membarrier_global_expedited(void)
static int membarrier_private_expedited(int flags)
{
int cpu;
bool fallback = false;
cpumask_var_t tmpmask;
struct mm_struct *mm = current->mm;
@ -168,15 +156,8 @@ static int membarrier_private_expedited(int flags)
*/
smp_mb(); /* system call entry is not a mb. */
/*
* Expedited membarrier commands guarantee that they won't
* block, hence the GFP_NOWAIT allocation flag and fallback
* implementation.
*/
if (!zalloc_cpumask_var(&tmpmask, GFP_NOWAIT)) {
/* Fallback for OOM. */
fallback = true;
}
if (!zalloc_cpumask_var(&tmpmask, GFP_KERNEL))
return -ENOMEM;
cpus_read_lock();
rcu_read_lock();
@ -195,20 +176,16 @@ static int membarrier_private_expedited(int flags)
continue;
rcu_read_lock();
p = rcu_dereference(cpu_rq(cpu)->curr);
if (p && p->mm == mm) {
if (!fallback)
__cpumask_set_cpu(cpu, tmpmask);
else
smp_call_function_single(cpu, ipi_mb, NULL, 1);
}
if (p && p->mm == mm)
__cpumask_set_cpu(cpu, tmpmask);
}
rcu_read_unlock();
if (!fallback) {
preempt_disable();
smp_call_function_many(tmpmask, ipi_mb, NULL, 1);
preempt_enable();
free_cpumask_var(tmpmask);
}
preempt_disable();
smp_call_function_many(tmpmask, ipi_mb, NULL, 1);
preempt_enable();
free_cpumask_var(tmpmask);
cpus_read_unlock();
/*
@ -264,7 +241,7 @@ static int sync_runqueues_membarrier_state(struct mm_struct *mm)
struct rq *rq = cpu_rq(cpu);
struct task_struct *p;
p = rcu_dereference(&rq->curr);
p = rcu_dereference(rq->curr);
if (p && p->mm == mm)
__cpumask_set_cpu(cpu, tmpmask);
}