Commit 4e018b45 authored Jun 11, 2020 by Naoya Horiguchi Committed by Linus Torvalds Jun 11, 2020

mm/memory-failure: prioritize prctl(PR_MCE_KILL) over vm.memory_failure_early_kill



Patch series "hwpoison: fixes signaling on memory error"

This is a small patchset to solve issues in memory error handler to send
SIGBUS to proper process/thread as expected in configuration.  Please
see descriptions in individual patches for more details.

This patch (of 2):

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@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Link: http://lkml.kernel.org/r/1591321039-22141-1-git-send-email-naoya.horiguchi@nec.com
Link: http://lkml.kernel.org/r/1591321039-22141-2-git-send-email-naoya.horiguchi@nec.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 623f6dc5

mm/memory-failure.c

+10 −10

Original line number	Diff line number	Diff line
		@@ -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))
		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);
		}

		/*

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