[PATCH v6 17/18] mm/memory-failure: increase queued recovery work's priority

James Morse
2018-09-21T22:19:06Z

arm64 can take an NMI-like error notification when user-space steps in
some corrupt memory. APEI's GHES code will call memory_failure_queue()
to schedule the recovery work. We then return to user-space, possibly
taking the fault again.

Currently the arch code unconditionally signals user-space from this
path, so we don't get stuck in this loop, but the affected process
never benefits from memory_failure()s recovery work. To fix this we
need to know the recovery work will run before we get back to user-space.

Increase the priority of the recovery work by scheduling it on the
system_highpri_wq, then try to bump the current task off this CPU
so that the recovery work starts immediately.

Reported-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Punit Agrawal <punit.agrawal@arm.com>
Tested-by: Tyler Baicar <tbaicar@codeaurora.org>
Tested-by: gengdongjiu <gengdongjiu@huawei.com>
CC: Xie XiuQi <xiexiuqi@huawei.com>
CC: gengdongjiu <gengdongjiu@huawei.com>
---
mm/memory-failure.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 0cd3de3550f0..4e7b115cea5a 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -56,6 +56,7 @@
#include <linux/memory_hotplug.h>
#include <linux/mm_inline.h>
#include <linux/memremap.h>
+#include <linux/preempt.h>
#include <linux/kfifo.h>
#include <linux/ratelimit.h>
#include <linux/page-isolation.h>
@@ -1454,6 +1455,7 @@ static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu);
*/
void memory_failure_queue(unsigned long pfn, int flags)
{
+ int cpu = smp_processor_id();
struct memory_failure_cpu *mf_cpu;
unsigned long proc_flags;
struct memory_failure_entry entry = {
@@ -1463,11 +1465,14 @@ void memory_failure_queue(unsigned long pfn, int flags)

mf_cpu = &get_cpu_var(memory_failure_cpu);
spin_lock_irqsave(&mf_cpu->lock, proc_flags);
- if (kfifo_put(&mf_cpu->fifo, entry))
- schedule_work_on(smp_processor_id(), &mf_cpu->work);
- else
+ if (kfifo_put(&mf_cpu->fifo, entry)) {
+ queue_work_on(cpu, system_highpri_wq, &mf_cpu->work);
+ set_tsk_need_resched(current);
+ preempt_set_need_resched();
+ } else {
pr_err("Memory failure: buffer overflow when queuing memory failure at %#lx\n",
pfn);
+ }
spin_unlock_irqrestore(&mf_cpu->lock, proc_flags);
put_cpu_var(memory_failure_cpu);
}
--
2.19.0