Early-kill policy is controlled from two types of settings, one is
per-process setting prctl(PR_MCE_KILL) and the other is system-wide setting
vm.memory_failure_early_kill. Users expect per-process setting to override
system-wide setting as many other settings do, but early-kill setting doesn't
work as such. For example, if a system configures
vm.memory_failure_early_kill to 1 (enabled), a process receives SIGBUS even
if it's configured to explicitly disable PF_MCE_KILL by prctl(). That's not
desirable for applications with their own policies.
This patch is suggesting to change the priority of these two types of settings,
by checking sysctl_memory_failure_early_kill only when a given process has the
default kill policy.
Note that this patch is solving a thread choice issue too. Originally,
collect_procs() always chooses the main thread when
vm.memory_failure_early_kill is 1, even if the process has a dedicated
thread for memory error handling. SIGBUS should be sent to the dedicated
thread if early-kill is enabled via vm.memory_failure_early_kill as we
are doing for PR_MCE_KILL_EARLY processes.
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
---
mm/memory-failure.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
diff --git v5.7/mm/memory-failure.c v5.7_patched/mm/memory-failure.c
index dd3862f..339c07d 100644
--- v5.7/mm/memory-failure.c
+++ v5.7_patched/mm/memory-failure.c
@@ -402,9 +402,15 @@ static struct task_struct *find_early_kill_thread(struct task_struct *tsk)
{
struct task_struct *t;
- for_each_thread(tsk, t)
- if ((t->flags & PF_MCE_PROCESS) && (t->flags & PF_MCE_EARLY))
- return t;
+ for_each_thread(tsk, t) {
+ if (t->flags & PF_MCE_PROCESS) {
+ if (t->flags & PF_MCE_EARLY)
+ return t;
+ } else {
+ if (sysctl_memory_failure_early_kill)
+ return t;
+ }
+ }
return NULL;
}
@@ -417,17 +423,11 @@ static struct task_struct *find_early_kill_thread(struct task_struct *tsk)
static struct task_struct *task_early_kill(struct task_struct *tsk,
int force_early)
{
- struct task_struct *t;
if (!tsk->mm)
return NULL;
if (force_early)
return tsk;
- t = find_early_kill_thread(tsk);
- if (t)
- return t;
- if (sysctl_memory_failure_early_kill)
- return tsk;
- return NULL;
+ return find_early_kill_thread(tsk);
}
/*
--
2.7.0
