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mm, oom: force oom kill on sysrq+f 

The oom killer chooses not to kill a thread if:

 - an eligible thread has already been oom killed and has yet to exit,
   and

 - an eligible thread is exiting but has yet to free all its memory and
   is not the thread attempting to currently allocate memory.

SysRq+F manually invokes the global oom killer to kill a memory-hogging
task.  This is normally done as a last resort to free memory when no
progress is being made or to test the oom killer itself.

For both uses, we always want to kill a thread and never defer.  This
patch causes SysRq+F to always kill an eligible thread and can be used to
force a kill even if another oom killed thread has failed to exit.

Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Rientjes 2012-03-21 16:34:04 -07:00 committed by Linus Torvalds
parent b76437579d
commit 08ab9b10d4
4 changed files with 13 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/tty/sysrq.c
View File

@ -346,7 +346,7 @@ static struct sysrq_key_op sysrq_term_op = {
static void moom_callback(struct work_struct *ignored)
{
out_of_memory(node_zonelist(0, GFP_KERNEL), GFP_KERNEL, 0, NULL);
out_of_memory(node_zonelist(0, GFP_KERNEL), GFP_KERNEL, 0, NULL, true);
}
static DECLARE_WORK(moom_work, moom_callback);

2
include/linux/oom.h
View File

@ -49,7 +49,7 @@ extern int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_flags);
extern void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_flags);
extern void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
int order, nodemask_t *mask);
int order, nodemask_t *mask, bool force_kill);
extern int register_oom_notifier(struct notifier_block *nb);
extern int unregister_oom_notifier(struct notifier_block *nb);

17
mm/oom_kill.c
View File

@ -310,7 +310,7 @@ static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
*/
static struct task_struct *select_bad_process(unsigned int *ppoints,
unsigned long totalpages, struct mem_cgroup *memcg,
const nodemask_t *nodemask)
const nodemask_t *nodemask, bool force_kill)
{
struct task_struct *g, *p;
struct task_struct *chosen = NULL;
@ -336,7 +336,8 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
if (test_tsk_thread_flag(p, TIF_MEMDIE)) {
if (unlikely(frozen(p)))
__thaw_task(p);
return ERR_PTR(-1UL);
if (!force_kill)
return ERR_PTR(-1UL);
}
if (!p->mm)
continue;
@ -354,7 +355,7 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
if (p == current) {
chosen = p;
*ppoints = 1000;
} else {
} else if (!force_kill) {
/*
* If this task is not being ptraced on exit,
* then wait for it to finish before killing
@ -572,7 +573,7 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask)
check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0, NULL);
limit = mem_cgroup_get_limit(memcg) >> PAGE_SHIFT;
read_lock(&tasklist_lock);
p = select_bad_process(&points, limit, memcg, NULL);
p = select_bad_process(&points, limit, memcg, NULL, false);
if (p && PTR_ERR(p) != -1UL)
oom_kill_process(p, gfp_mask, 0, points, limit, memcg, NULL,
"Memory cgroup out of memory");
@ -687,6 +688,7 @@ static void clear_system_oom(void)
* @gfp_mask: memory allocation flags
* @order: amount of memory being requested as a power of 2
* @nodemask: nodemask passed to page allocator
* @force_kill: true if a task must be killed, even if others are exiting
*
* If we run out of memory, we have the choice between either
* killing a random task (bad), letting the system crash (worse)
@ -694,7 +696,7 @@ static void clear_system_oom(void)
* don't have to be perfect here, we just have to be good.
*/
void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
int order, nodemask_t *nodemask)
int order, nodemask_t *nodemask, bool force_kill)
{
const nodemask_t *mpol_mask;
struct task_struct *p;
@ -738,7 +740,8 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
goto out;
}
p = select_bad_process(&points, totalpages, NULL, mpol_mask);
p = select_bad_process(&points, totalpages, NULL, mpol_mask,
force_kill);
/* Found nothing?!?! Either we hang forever, or we panic. */
if (!p) {
dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
@ -770,7 +773,7 @@ out:
void pagefault_out_of_memory(void)
{
if (try_set_system_oom()) {
out_of_memory(NULL, 0, 0, NULL);
out_of_memory(NULL, 0, 0, NULL, false);
clear_system_oom();
}
if (!test_thread_flag(TIF_MEMDIE))

2
mm/page_alloc.c
View File

@ -1968,7 +1968,7 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
goto out;
}
/* Exhausted what can be done so it's blamo time */
out_of_memory(zonelist, gfp_mask, order, nodemask);
out_of_memory(zonelist, gfp_mask, order, nodemask, false);
out:
clear_zonelist_oom(zonelist, gfp_mask);