sysctl_panic_on_oom broken

sysctl_panic_on_oom broken

[Larry Woodman]

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out_of_memory() does not panic when sysctl_panic_on_oom is set
if constrained_alloc() does not return CONSTRAINT_NONE.  Instead,
out_of_memory() kills the current process whenever constrained_alloc()
returns either CONSTRAINT_MEMORY_POLICY or CONSTRAINT_CPUSET.
This patch fixes this problem:




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--- linux-2.6.18.noarch/mm/oom_kill.c.orig
+++ linux-2.6.18.noarch/mm/oom_kill.c
@@ -431,6 +437,9 @@ void out_of_memory(struct zonelist *zone
 	cpuset_lock();
 	read_lock(&tasklist_lock);
 
+	/* check if we are going to panic before enything else... */
+	if (sysctl_panic_on_oom)
+		panic("out of memory. panic_on_oom is selected\n");
 	/*
 	 * Check if there were limitations on the allocation (only relevant for
 	 * NUMA) that may require different handling.
@@ -447,8 +456,6 @@ void out_of_memory(struct zonelist *zone
 		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

Re: sysctl_panic_on_oom broken

[Christoph Lameter]

On Tue, 17 Apr 2007, Larry Woodman wrote:

> out_of_memory() does not panic when sysctl_panic_on_oom is set
> if constrained_alloc() does not return CONSTRAINT_NONE.  Instead,
> out_of_memory() kills the current process whenever constrained_alloc()
> returns either CONSTRAINT_MEMORY_POLICY or CONSTRAINT_CPUSET.
> This patch fixes this problem:

The patch recreates the problem that the system may OOM 
although lots of memory is still free. Constrained allocation means that 
the allocation was only to a portion of system memory. The rest may be 
free. No reason to oom.

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