Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754929AbbFRJ7E (ORCPT ); Thu, 18 Jun 2015 05:59:04 -0400 Received: from cantor2.suse.de ([195.135.220.15]:55989 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753950AbbFRJ5i (ORCPT ); Thu, 18 Jun 2015 05:57:38 -0400 From: Michal Hocko To: Andrew Morton Cc: David Rientjes , , LKML Subject: [PATCH 2/2] oom: split out forced OOM killer Date: Thu, 18 Jun 2015 11:57:27 +0200 Message-Id: <1434621447-21175-3-git-send-email-mhocko@suse.cz> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1434621447-21175-1-git-send-email-mhocko@suse.cz> References: <1434621447-21175-1-git-send-email-mhocko@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6778 Lines: 176 The forced OOM killing is currently wired into out_of_memory() call even though their objective is different which makes the code ugly and harder to follow. Generic out_of_memory path has to deal with configuration settings and heuristics which are completely irrelevant to the forced OOM killer (e.g. sysctl_oom_kill_allocating_task or OOM killer prevention for already dying tasks). All of them are either relying on explicit force_kill check or indirectly by checking current->mm which is always NULL for sysrq+f. This is not nice, hard to follow and error prone. Let's pull forced OOM killer code out into a separate function (force_out_of_memory) which is really trivial now. As a bonus we can clearly state that this is a forced OOM killer in the OOM message which is helpful to distinguish it from the regular OOM killer. Signed-off-by: Michal Hocko --- drivers/tty/sysrq.c | 3 +-- include/linux/oom.h | 3 ++- mm/oom_kill.c | 57 ++++++++++++++++++++++++++++++++--------------------- mm/page_alloc.c | 2 +- 4 files changed, 39 insertions(+), 26 deletions(-) diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 3a42b7187b8e..06a95a8ed701 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -356,8 +356,7 @@ static struct sysrq_key_op sysrq_term_op = { static void moom_callback(struct work_struct *ignored) { mutex_lock(&oom_lock); - if (!out_of_memory(node_zonelist(first_memory_node, GFP_KERNEL), - GFP_KERNEL, 0, NULL, true)) + if (!force_out_of_memory()) pr_info("OOM request ignored because killer is disabled\n"); mutex_unlock(&oom_lock); } diff --git a/include/linux/oom.h b/include/linux/oom.h index 7deecb7bca5e..061e0ffd3493 100644 --- a/include/linux/oom.h +++ b/include/linux/oom.h @@ -70,8 +70,9 @@ extern enum oom_scan_t oom_scan_process_thread(struct task_struct *task, unsigned long totalpages, const nodemask_t *nodemask, bool force_kill); +extern bool force_out_of_memory(void); extern bool out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, - int order, nodemask_t *mask, bool force_kill); + int order, nodemask_t *mask); extern void exit_oom_victim(void); diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 0c312eaac834..050936f35944 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -635,12 +635,38 @@ int unregister_oom_notifier(struct notifier_block *nb) EXPORT_SYMBOL_GPL(unregister_oom_notifier); /** - * __out_of_memory - kill the "best" process when we run out of memory + * force_out_of_memory - forces OOM killer + * + * External trigger for the OOM killer. The system doesn't have to be under + * OOM condition (e.g. sysrq+f). + */ +bool force_out_of_memory(void) +{ + struct zonelist *zonelist = node_zonelist(first_memory_node, GFP_KERNEL); + struct task_struct *p; + unsigned long totalpages; + unsigned int points; + + if (oom_killer_disabled) + return false; + + constrained_alloc(zonelist, GFP_KERNEL, NULL, &totalpages); + p = select_bad_process(&points, totalpages, NULL, true); + if (p != (void *)-1UL) + oom_kill_process(p, GFP_KERNEL, 0, points, totalpages, NULL, + NULL, "Forced out of memory killer"); + else + pr_warn("Forced out of memory. No killable task found...\n"); + + return true; +} + +/** + * out_of_memory - kill the "best" process when we run out of memory * @zonelist: zonelist pointer * @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) @@ -648,7 +674,7 @@ EXPORT_SYMBOL_GPL(unregister_oom_notifier); * don't have to be perfect here, we just have to be good. */ bool out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, - int order, nodemask_t *nodemask, bool force_kill) + int order, nodemask_t *nodemask) { const nodemask_t *mpol_mask; struct task_struct *p; @@ -687,14 +713,8 @@ bool out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, constraint = constrained_alloc(zonelist, gfp_mask, nodemask, &totalpages); mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL; - /* Ignore panic_on_oom when the OOM killer is sysrq triggered */ - if (!force_kill) - check_panic_on_oom(constraint, gfp_mask, order, mpol_mask, NULL); + check_panic_on_oom(constraint, gfp_mask, order, mpol_mask, NULL); - /* - * not affecting force_kill because sysrq triggered OOM killer runs from - * the workqueue context so current->mm will be NULL - */ if (sysctl_oom_kill_allocating_task && current->mm && !oom_unkillable_task(current, NULL, nodemask) && current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) { @@ -705,18 +725,11 @@ bool out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, goto out; } - p = select_bad_process(&points, totalpages, mpol_mask, force_kill); - /* - * Found nothing?!?! Either we hang forever, or we panic. - * Do not panic when the OOM killer is sysrq triggered. - */ + p = select_bad_process(&points, totalpages, mpol_mask, false); + /* Found nothing?!?! Either we hang forever, or we panic. */ if (!p) { - if (!force_kill) { - dump_header(NULL, gfp_mask, order, NULL, mpol_mask); - panic("Out of memory and no killable processes...\n"); - } else { - pr_info("Forced out of memory. No killable task found...\n"); - } + dump_header(NULL, gfp_mask, order, NULL, mpol_mask); + panic("Out of memory and no killable processes...\n"); } if (p != (void *)-1UL) { oom_kill_process(p, gfp_mask, order, points, totalpages, NULL, @@ -747,7 +760,7 @@ void pagefault_out_of_memory(void) if (!mutex_trylock(&oom_lock)) return; - if (!out_of_memory(NULL, 0, 0, NULL, false)) { + if (!out_of_memory(NULL, 0, 0, NULL)) { /* * There shouldn't be any user tasks runnable while the * OOM killer is disabled, so the current task has to diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 1f9ffbb087cb..014806d13138 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2731,7 +2731,7 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order, goto out; } /* Exhausted what can be done so it's blamo time */ - if (out_of_memory(ac->zonelist, gfp_mask, order, ac->nodemask, false) + if (out_of_memory(ac->zonelist, gfp_mask, order, ac->nodemask) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) *did_some_progress = 1; out: -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/