linux-kernel - [28/98] sched: Fix isolcpus boot option

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Date:	Tue, 26 Jan 2010 15:33:54 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Rusty Russell <rusty@...tcorp.com.au>, peterz@...radead.org,
	Ingo Molnar <mingo@...e.hu>
Subject: [28/98] sched: Fix isolcpus boot option

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Rusty Russell <rusty@...tcorp.com.au>

commit bdddd2963c0264c56f18043f6fa829d3c1d3d1c0 upstream.

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@...ba.org>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
Cc: peterz@...radead.org
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: <stable@...nel.org>
LKML-Reference: <200912021409.17013.rusty@...tcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Tested-by: Anton Blanchard <anton@...ba.org>

---
 kernel/sched.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -8061,6 +8061,7 @@ 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;
 }
@@ -9591,7 +9592,9 @@ 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();


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