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Commit 071a4bef authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds
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mm, oom: do not panic for oom kills triggered from sysrq 



Sysrq+f is used to kill a process either for debug or when the VM is
otherwise unresponsive.

It is not intended to trigger a panic when no process may be killed.

Avoid panicking the system for sysrq+f when no processes are killed.

Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
Suggested-by: default avatarMichal Hocko <mhocko@suse.cz>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 54e9e291

Documentation/sysrq.txt

+2 −1
Original line number Diff line number Diff line
@@ -75,7 +75,8 @@ On all - write a character to /proc/sysrq-trigger. e.g.: 


'e'     - Send a SIGTERM to all processes, except for init.



'f'	- Will call oom_kill to kill a memory hog process.

'f'	- Will call the oom killer to kill a memory hog process, but do not

	  panic if nothing can be killed.



'g'	- Used by kgdb (kernel debugger)

mm/oom_kill.c

+5 −2
Original line number Diff line number Diff line
@@ -607,6 +607,9 @@ void check_panic_on_oom(struct oom_control *oc, enum oom_constraint constraint, 
		if (constraint != CONSTRAINT_NONE)

			return;

	}

	/* Do not panic for oom kills triggered by sysrq */

	if (oc->order == -1)

		return;

	dump_header(oc, NULL, memcg);

	panic("Out of memory: %s panic_on_oom is enabled\n",

		sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
@@ -686,11 +689,11 @@ bool out_of_memory(struct oom_control *oc) 


	p = select_bad_process(oc, &points, totalpages);

	/* Found nothing?!?! Either we hang forever, or we panic. */

	if (!p) {

	if (!p && oc->order != -1) {

		dump_header(oc, NULL, NULL);

		panic("Out of memory and no killable processes...\n");

	}

	if (p != (void *)-1UL) {

	if (p && p != (void *)-1UL) {

		oom_kill_process(oc, p, points, totalpages, NULL,

				 "Out of memory");

		killed = 1;