Re: [PATCH] [ARM] Unconditional call to smp_cross_call on UP crashes(take #2)

From: Shawn Guo
Date: Fri May 25 2012 - 02:43:31 EST


On Fri, May 25, 2012 at 07:58:36PM +0000, Pantelis Antoniou wrote:
> omap2plus_defconfig builds with SMP & SMP_ON_UP set.
> On beagle (which is UP) is_smp() returns false and we don't call
> smp_init_cpus which in turn does not initialize smp_cross_call which
> remains NULL.
>
> When issuing a reboot we OOPS with a NULL dereference on stop smp_call.
>
> Fixed by a check with if (!cpumask_empty(&mask)) before issuing the smp
> stop cross call.
>
I can reproduce the issue on imx5 built from imx_v6_v7_defconfig, and
see the patch fix it here. Thus,

Tested-by: Shawn Guo <shawn.guo@xxxxxxxxxx>

Regards,
Shawn

> Restarting system.
> Unable to handle kernel NULL pointer dereference at virtual address 00000000
> pgd = dda50000
> [00000000] *pgd=9e723831, *pte=00000000, *ppte=00000000
> Internal error: Oops: 80000007 [#1] SMP ARM
> Modules linked in:
> CPU: 0 Not tainted (3.4.0-00001-gb15b046 #30)
> PC is at 0x0
> LR is at smp_send_stop+0x4c/0xe8
> pc : [<00000000>] lr : [<c00188cc>] psr: 60000013
> sp : de7b5e70 ip : 00000000 fp : 00000001
> r10: 00000000 r9 : de7b4000 r8 : c07263d0
> r7 : 00000000 r6 : c06e1294 r5 : 000f4240 r4 : de7b5e74
> r3 : 00000000 r2 : 00000000 r1 : 00000006 r0 : de7b5e74
> Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
> Control: 10c5387d Table: 9da50019 DAC: 00000015
> Process reboot (pid: 2229, stack limit = 0xde7b42f8)
> Stack: (0xde7b5e70 to 0xde7b6000)
> 5e60: 00000000 00000000 00000000 01234567
> 5e80: de7b4000 c001475c 4321fedc c0052570 0000003e 00000000 c081db78 0000003e
> 5ea0: 00000001 00000002 00000002 c00891f0 00000002 dd5ba0ac 00000002 00000000
> 5ec0: dd5ba0ac de7b4000 c009eef4 de7b4000 c00f44dc de7b4000 c00f44dc 00000000
> 5ee0: c0c94d24 de7b4000 00000000 00000000 00000002 00000002 00000000 c00891f0
> 5f00: 00000002 00000000 00000000 c011286c 00000000 dd5ba060 60000013 00000000
> 5f20: dd688d8c 00000000 de7b4000 c06e20f8 dec14760 dec14750 de7b4000 c06e20f8
> 5f40: 00011f10 c01128a0 00000002 00000000 c011286c c00fa014 dd8c3180 de7b4000
> 5f60: c0013380 de508bc0 00000001 60000010 00000001 ef000000 00000001 c0089bfc
> 5f80: 00000000 00000001 00000004 00000058 00000000 00000001 00000004 00000058
> 5fa0: c0013428 c0013260 00000000 00000001 fee1dead 28121969 01234567 00000000
> 5fc0: 00000000 00000001 00000004 00000058 00000001 00000001 00000000 00000001
> 5fe0: b6e76200 beba4c90 00009210 b6e76218 60000010 fee1dead 00000000 00000000
> [<c00188cc>] (smp_send_stop+0x4c/0xe8) from [<c001475c>] (machine_restart+0xc/0x54)
> [<c001475c>] (machine_restart+0xc/0x54) from [<c0052570>] (sys_reboot+0x140/0x204)
> [<c0052570>] (sys_reboot+0x140/0x204) from [<c0013260>] (ret_fast_syscall+0x0/0x3c)
> Code: bad PC value
> ---[ end trace f5035e8726d1f51b ]---
>
> Signed-off-by: Pantelis Antoniou <panto@xxxxxxxxxxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> arch/arm/kernel/smp.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
> index 8f46446..7babc3f 100644
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -590,7 +590,8 @@ void smp_send_stop(void)
>
> cpumask_copy(&mask, cpu_online_mask);
> cpumask_clear_cpu(smp_processor_id(), &mask);
> - smp_cross_call(&mask, IPI_CPU_STOP);
> + if (!cpumask_empty(&mask))
> + smp_cross_call(&mask, IPI_CPU_STOP);
>
> /* Wait up to one second for other CPUs to stop */
> timeout = USEC_PER_SEC;
> --
> 1.7.1
>
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