sysctl_panic_on_oom broken

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:

@@ -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

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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