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Commit 309ed882 authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds
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oom: extract panic helper function 



There are various points in the oom killer where the kernel must determine
whether to panic or not.  It's better to extract this to a helper function
to remove all the confusion as to its semantics.

Also fix a call to dump_header() where tasklist_lock is not read- locked,
as required.

There's no functional change with this patch.

Acked-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 03668b3c

include/linux/oom.h

+1 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ enum oom_constraint { 
	CONSTRAINT_NONE,

	CONSTRAINT_CPUSET,

	CONSTRAINT_MEMORY_POLICY,

	CONSTRAINT_MEMCG,

};



extern int try_set_zone_oom(struct zonelist *zonelist, gfp_t gfp_flags);

mm/oom_kill.c

+29 −24
Original line number Diff line number Diff line
@@ -521,17 +521,40 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, 
	return oom_kill_task(victim);

}



/*

 * Determines whether the kernel must panic because of the panic_on_oom sysctl.

 */

static void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask,

				int order)

{

	if (likely(!sysctl_panic_on_oom))

		return;

	if (sysctl_panic_on_oom != 2) {

		/*

		 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel

		 * does not panic for cpuset, mempolicy, or memcg allocation

		 * failures.

		 */

		if (constraint != CONSTRAINT_NONE)

			return;

	}

	read_lock(&tasklist_lock);

	dump_header(NULL, gfp_mask, order, NULL);

	read_unlock(&tasklist_lock);

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

		sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");

}



#ifdef CONFIG_CGROUP_MEM_RES_CTLR

void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)

{

	unsigned long points = 0;

	struct task_struct *p;



	if (sysctl_panic_on_oom == 2)

		panic("out of memory(memcg). panic_on_oom is selected.\n");

	check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0);

	read_lock(&tasklist_lock);

retry:

	p = select_bad_process(&points, mem, CONSTRAINT_NONE, NULL);

	p = select_bad_process(&points, mem, CONSTRAINT_MEMCG, NULL);

	if (!p || PTR_ERR(p) == -1UL)

		goto out;
@@ -632,8 +655,8 @@ static void __out_of_memory(gfp_t gfp_mask, int order, 


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

	if (!p) {

		read_unlock(&tasklist_lock);

		dump_header(NULL, gfp_mask, order, NULL);

		read_unlock(&tasklist_lock);

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

	}
@@ -655,9 +678,7 @@ void pagefault_out_of_memory(void) 
		/* Got some memory back in the last second. */

		return;



	if (sysctl_panic_on_oom)

		panic("out of memory from page fault. panic_on_oom is selected.\n");



	check_panic_on_oom(CONSTRAINT_NONE, 0, 0);

	read_lock(&tasklist_lock);

	/* unknown gfp_mask and order */

	__out_of_memory(0, 0, CONSTRAINT_NONE, NULL);
@@ -704,29 +725,13 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, 
		return;

	}



	if (sysctl_panic_on_oom == 2) {

		dump_header(NULL, gfp_mask, order, NULL);

		panic("out of memory. Compulsory panic_on_oom is selected.\n");

	}



	/*

	 * Check if there were limitations on the allocation (only relevant for

	 * NUMA) that may require different handling.

	 */

	constraint = constrained_alloc(zonelist, gfp_mask, nodemask);

	check_panic_on_oom(constraint, gfp_mask, order);

	read_lock(&tasklist_lock);

	if (unlikely(sysctl_panic_on_oom)) {

		/*

		 * panic_on_oom only affects CONSTRAINT_NONE, the kernel

		 * should not panic for cpuset or mempolicy induced memory

		 * failures.

		 */

		if (constraint == CONSTRAINT_NONE) {

			dump_header(NULL, gfp_mask, order, NULL);

			read_unlock(&tasklist_lock);

			panic("Out of memory: panic_on_oom is enabled\n");

		}

	}

	__out_of_memory(gfp_mask, order, constraint, nodemask);

	read_unlock(&tasklist_lock);