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@xxxxxxxxxx>
---
drivers/tty/sysrq.c | 2 +-
include/linux/oom.h | 2 +-
mm/oom_kill.c | 17 ++++++++++-------
mm/page_alloc.c | 2 +-
4 files changed, 13 insertions(+), 10 deletions(-)
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -343,7 +343,7 @@ 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);
diff --git a/include/linux/oom.h b/include/linux/oom.h
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -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);
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -309,7 +309,7 @@ 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;
@@ -335,7 +335,8 @@ 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;
@@ -353,7 +354,7 @@ 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
@@ -581,7 +582,7 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask)
limit = mem_cgroup_get_limit(memcg) >> PAGE_SHIFT;
read_lock(&tasklist_lock);
retry:
- p = select_bad_process(&points, limit, memcg, NULL);
+ p = select_bad_process(&points, limit, memcg, NULL, false);
if (!p || PTR_ERR(p) == -1UL)
goto out;
@@ -700,6 +701,7 @@ 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)
@@ -707,7 +709,7 @@ 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;
@@ -757,7 +759,8 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
}
retry:
- p = select_bad_process(&points, totalpages, NULL, mpol_mask);
+ p = select_bad_process(&points, totalpages, NULL, mpol_mask,
+ force_kill);
if (PTR_ERR(p) == -1UL)
goto out;
@@ -792,7 +795,7 @@ 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))
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -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);
--
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