[PATCH] support for panic at OOM

This patch adds panic_on_oom sysctl under sys.vm.

When sysctl vm.panic_on_oom = 1, the kernel panics intead of killing rogue
processes.  And if vm.panic_on_oom is 0 the kernel will do oom_kill() in
the same way as it does today.  Of course, the default value is 0 and only
root can modifies it.

In general, oom_killer works well and kill rogue processes.  So the whole
system can survive.  But there are environments where panic is preferable
rather than kill some processes.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Documentation/sysctl/vm.txt

@@ -29,6 +29,7 @@ Currently, these files are in /proc/sys/vm:
 - drop-caches
 - zone_reclaim_mode
 - zone_reclaim_interval
+- panic_on_oom
 
 ==============================================================
 
@@ -178,3 +179,15 @@ Time is set in seconds and set by default to 30 seconds.
 Reduce the interval if undesired off node allocations occur. However, too
 frequent scans will have a negative impact onoff node allocation performance.
 
+=============================================================
+
+panic_on_oom
+
+This enables or disables panic on out-of-memory feature.  If this is set to 1,
+the kernel panics when out-of-memory happens.  If this is set to 0, the kernel
+will kill some rogue process, called oom_killer.  Usually, oom_killer can kill
+rogue processes and system will survive.  If you want to panic the system
+rather than killing rogue processes, set this to 1.
+
+The default value is 0.
+

include/linux/sysctl.h

@@ -186,6 +186,7 @@ enum
 	VM_PERCPU_PAGELIST_FRACTION=30,/* int: fraction of pages in each percpu_pagelist */
 	VM_ZONE_RECLAIM_MODE=31, /* reclaim local zone memory before going off node */
 	VM_ZONE_RECLAIM_INTERVAL=32, /* time period to wait after reclaim failure */
+	VM_PANIC_ON_OOM=33,	/* panic at out-of-memory */
 };
 
 

kernel/sysctl.c

@@ -59,6 +59,7 @@ extern int proc_nr_files(ctl_table *table, int write, struct file *filp,
 extern int C_A_D;
 extern int sysctl_overcommit_memory;
 extern int sysctl_overcommit_ratio;
+extern int sysctl_panic_on_oom;
 extern int max_threads;
 extern int sysrq_enabled;
 extern int core_uses_pid;
@@ -701,6 +702,14 @@ static ctl_table vm_table[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec,
 	},
+	{
+		.ctl_name	= VM_PANIC_ON_OOM,
+		.procname	= "panic_on_oom",
+		.data		= &sysctl_panic_on_oom,
+		.maxlen		= sizeof(sysctl_panic_on_oom),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
 	{
 		.ctl_name	= VM_OVERCOMMIT_RATIO,
 		.procname	= "overcommit_ratio",

mm/oom_kill.c

@@ -22,6 +22,7 @@
 #include <linux/jiffies.h>
 #include <linux/cpuset.h>
 
+int sysctl_panic_on_oom;
 /* #define DEBUG */
 
 /**
@@ -344,6 +345,8 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, int order)
 		break;
 
 	case CONSTRAINT_NONE:
+		if (sysctl_panic_on_oom)
+			panic("out of memory. panic_on_oom is selected\n");
 retry:
 		/*
 		 * Rambo mode: Shoot down a process and hope it solves whatever