Messages in this thread Patch in this message | | | Date | Wed, 19 Jan 2011 21:53:53 +0100 | From | Ingo Molnar <> | Subject | Re: percpu related boot crash on x86 (was: Linux 2.6.38-rc1) |
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* Tejun Heo <tj@kernel.org> wrote:
> Hello, > > On Wed, Jan 19, 2011 at 02:56:23PM +0200, Pekka Enberg wrote: > > Is vmalloc() and vfree() supposed to work with interrupts disabled? I > > always thought they weren't which would mean something in > > pcpu_mem_alloc() needs changing... > > They aren't but percpu allocator doesn't call them with interrupts > disabled normally. It only happens during early boot before it's > enabled for the first time but this is an allowed exception. We'll > probably need to update the WARN_ON to consider the rare call path. > It also looks like something in that path is turning off/on IRQ > instead of saving/restoring it, so that probably needs to be changed > too but both aren't really critical. > > I think the real problem is a lot of unsigned int percpu allocations > added by 6c9ae009 (irq: use per_cpu kstat_irqs). percpu allocator > should be able to cope but it assumes that it would always be able to > allocate contiguous allocation map using vmalloc and that might be > failing, although I cannot readily see how or why that would happen > frequently on a 64bit machine.
Btw., based on Peter's suggestion i tried the limit-bumping hack below - but it did not help, the crash still triggers on 5%-10% of all randconfig bootups.
Thanks,
Ingo
From e2c013d28c8fe81cd30976dcd3058cc86c6285d3 Mon Sep 17 00:00:00 2001 From: Ingo Molnar <mingo@elte.hu> Date: Wed, 19 Jan 2011 20:15:20 +0100 Subject: [PATCH] <not for upstream> percpu: Increase allocation limits
Might solve the boot crashes ...
Signed-off-by: Ingo Molnar <mingo@elte.hu> --- mm/percpu.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/mm/percpu.c b/mm/percpu.c index 3f93001..5cd9cf4 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -74,7 +74,7 @@ #include <asm/io.h> #define PCPU_SLOT_BASE_SHIFT 5 /* 1-31 shares the same slot */ -#define PCPU_DFL_MAP_ALLOC 16 /* start a map with 16 ents */ +#define PCPU_DFL_MAP_ALLOC 64 /* start a map with 64 ents */ #ifdef CONFIG_SMP /* default addr <-> pcpu_ptr mapping, override in asm/percpu.h if necessary */
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