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

[Shawn Guo]

Hi Pantelis,

In case you do not know the process of ARM core patches.  You need to
put the patch into Russell's patch system [1] after review gets done.
Then the patch will show up on Russell's git tree.

Regards,
Shawn

[1] http://www.arm.linux.org.uk/developer/patches/

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.
> 
> 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 at antoniou-consulting.com>
> Cc: stable at vger.kernel.org
> ---
>  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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