linux-kernel - Re: [patch 1/4] x86, ioapic: fix potential resume deadlock

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Date:	Mon, 16 May 2011 20:53:09 +0100
From:	Daniel J Blueman <daniel.blueman@...il.com>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	mingo@...e.hu, tglx@...utronix.de, hpa@...or.com,
	linux-kernel@...r.kernel.org, stable@...nel.org
Subject: Re: [patch 1/4] x86, ioapic: fix potential resume deadlock

On 16 May 2011 19:56, Suresh Siddha <suresh.b.siddha@...el.com> wrote:
> From: Daniel J Blueman <daniel.blueman@...il.com>
> Subject: x86, ioapic: fix potential resume deadlock
>
> Fix a potential deadlock when resuming; here the calling function
> has disabled interrupts, so we cannot sleep.
>
> Change the memory allocation flag from GFP_KERNEL to GFP_ATOMIC.
>
> TODO: We can do away with this memory allocation during resume by
> reusing the ioapic suspend/resume code that uses boot time allocated
> buffers.
>
> Signed-off-by: Daniel J Blueman <daniel.blueman@...il.com>
> Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
> Cc: stable@...nel.org   [v2.6.39]
> ---
>  arch/x86/kernel/apic/io_apic.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> Index: linux-2.6-tip/arch/x86/kernel/apic/io_apic.c
> ===================================================================
> --- linux-2.6-tip.orig/arch/x86/kernel/apic/io_apic.c
> +++ linux-2.6-tip/arch/x86/kernel/apic/io_apic.c
> @@ -621,14 +621,14 @@ struct IO_APIC_route_entry **alloc_ioapi
>        struct IO_APIC_route_entry **ioapic_entries;
>
>        ioapic_entries = kzalloc(sizeof(*ioapic_entries) * nr_ioapics,
> -                               GFP_KERNEL);
> +                               GFP_ATOMIC);
>        if (!ioapic_entries)
>                return 0;
>
>        for (apic = 0; apic < nr_ioapics; apic++) {
>                ioapic_entries[apic] =
>                        kzalloc(sizeof(struct IO_APIC_route_entry) *
> -                               nr_ioapic_registers[apic], GFP_KERNEL);
> +                               nr_ioapic_registers[apic], GFP_ATOMIC);
>                if (!ioapic_entries[apic])
>                        goto nomem;
>        }

I just tested this patch series (1-3) and it does addresses the resume
allocation failures I was consistently seeing (triggering your
warning); it passes nicely with full lock, allocation etc debugging,
so looks all good. Tested-by: Daniel J Blueman
<daniel.blueman@...il.com>

Thanks, Suresh!

Daniel
-- 
Daniel J Blueman
--
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