[PATCH] sched: Fix isolcpus boot option

[Rusty Russell <rusty@rustcorp.com.au>]

On Mon, 30 Nov 2009 10:35:32 am Anton Blanchard wrote:
> We allocate and zero cpu_isolated_map after the isolcpus __setup option
> has run. This means cpu_isolated_map always ends up empty and if
> CPUMASK_OFFSTACK is enabled we write to a cpumask that hasn't been
> allocated.

I introduced this regression in 49557e620339cb13 (sched: Fix boot
crash by zalloc()ing most of the cpu masks).

Use the bootmem allocator if they set isolcpus=, otherwise allocate
and zero like normal.

Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Tested-by: Anton Blanchard <anton@samba.org>
Cc: stable@kernel.org

diff --git a/kernel/sched.c b/kernel/sched.c
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -8045,6 +8045,7 @@ static cpumask_var_t cpu_isolated_map;
 /* Setup the mask of cpus configured for isolated domains */
 static int __init isolated_cpu_setup(char *str)
 {
+	alloc_bootmem_cpumask_var(&cpu_isolated_map);
 	cpulist_parse(str, cpu_isolated_map);
 	return 1;
 }
@@ -9571,7 +9572,9 @@ void __init sched_init(void)
 	zalloc_cpumask_var(&nohz.cpu_mask, GFP_NOWAIT);
 	alloc_cpumask_var(&nohz.ilb_grp_nohz_mask, GFP_NOWAIT);
 #endif
-	zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
+	/* May be allocated at isolcpus cmdline parse time */
+	if (cpu_isolated_map == NULL)
+		zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
 #endif /* SMP */
 
 	perf_event_init();