[PATCH 1/1] ARM: only call smp_send_stop() on SMP

Thu Jun 28 03:06:23 EDT 2012

Err,

There was a patch been sent in response that did exactly as you asked.

http://lkml.indiana.edu/hypermail/linux/kernel/1205.3/00433.html

Regards

-- Pantelis

On Jun 24, 2012, at 11:59 AM, Russell King - ARM Linux wrote:

> See this thread:
> 
> http://lists.arm.linux.org.uk/lurker/thread/20120523.200015.2fdfd505.en.html
> 
> There are times when I wonder why I bother replying to email on mailing
> lists.  No patch ever came from my responses on this subject.  Not going
> to repeat it again.  Fed up.
> 
> On Sun, Jun 24, 2012 at 06:21:07AM +0200, Javier Martinez Canillas wrote:
>> On reboot or poweroff (machine_shutdown()) a call to smp_send_stop() is
>> made (to stop the others CPU's) when CONFIG_SMP=y.
>> 
>> arch/arm/kernel/process.c:
>> 
>> void machine_shutdown(void)
>> {
>> #ifdef CONFIG_SMP
>>       smp_send_stop();
>> #endif
>> }
>> 
>> smp_send_stop() calls the function pointer smp_cross_call(), which is set
>> on the smp_init_cpus() function for OMAP processors.
>> 
>> arch/arm/mach-omap2/omap-smp.c:
>> 
>> void __init smp_init_cpus(void)
>> {
>> ...
>> 	set_smp_cross_call(gic_raise_softirq);
>> ...
>> }
>> 
>> But the ARM setup_arch() function only calls smp_init_cpus()
>> if CONFIG_SMP=y && is_smp().
>> 
>> arm/kernel/setup.c:
>> 
>> void __init setup_arch(char **cmdline_p)
>> {
>> ...
>> #ifdef CONFIG_SMP
>> 	if (is_smp())
>> 		smp_init_cpus();
>> #endif
>> ...
>> }
>> 
>> Newer OMAP CPU's are SMP machines so omap2plus_defconfig sets
>> CONFIG_SMP=y. Unfortunately on an OMAP UP machine is_smp()
>> returns false and smp_init_cpus() is never called and the
>> smp_cross_call() function remains NULL.
>> 
>> If the machine is rebooted or powered off, smp_send_stop() will
>> be called (since CONFIG_SMP=y) leading to the following error:
>> 
>> [   42.815551] Restarting system.
>> [   42.819030] Unable to handle kernel NULL pointer dereference at virtual address 00000000
>> [   42.827667] pgd = d7a74000
>> [   42.830566] [00000000] *pgd=96ce7831, *pte=00000000, *ppte=00000000
>> [   42.837249] Internal error: Oops: 80000007 [#1] SMP ARM
>> [   42.842773] Modules linked in:
>> [   42.846008] CPU: 0    Not tainted  (3.5.0-rc3-next-20120622-00002-g62e87ba-dirty #44)
>> [   42.854278] PC is at 0x0
>> [   42.856994] LR is at smp_send_stop+0x4c/0xe4
>> [   42.861511] pc : [<00000000>]    lr : [<c00183a4>]    psr: 60000013
>> [   42.861511] sp : d6c85e70  ip : 00000000  fp : 00000000
>> [   42.873626] r10: 00000000  r9 : d6c84000  r8 : 00000002
>> [   42.879150] r7 : c07235a0  r6 : c06dd2d0  r5 : 000f4241  r4 : d6c85e74
>> [   42.886047] r3 : 00000000  r2 : 00000000  r1 : 00000006  r0 : d6c85e74
>> [   42.892944] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
>> [   42.900482] Control: 10c5387d  Table: 97a74019  DAC: 00000015
>> [   42.906555] Process reboot (pid: 1166, stack limit = 0xd6c842f8)
>> [   42.912902] Stack: (0xd6c85e70 to 0xd6c86000)
>> [   42.917510] 5e60:                                     c07235a0 00000000 00000000 d6c84000
>> [   42.926177] 5e80: 01234567 c00143d0 4321fedc c00511bc d6c85ebc 00000168 00000460 00000000
>> [   42.934814] 5ea0: c1017950 a0000013 c1017900 d8014390 d7ec3858 c0498e48 c1017950 00000000
>> [   42.943481] 5ec0: d6ddde10 d6c85f78 00000003 00000000 d6ddde10 d6c84000 00000000 00000000
>> [   42.952117] 5ee0: 00000002 00000000 00000000 c0088c88 00000002 00000000 00000000 c00f4b90
>> [   42.960784] 5f00: 00000000 d6c85ebc d8014390 d7e311c8 60000013 00000103 00000002 d6c84000
>> [   42.969421] 5f20: c00f3274 d6e00a00 00000001 60000013 d6c84000 00000000 00000000 c00895d4
>> [   42.978057] 5f40: 00000002 d8007c80 d781f000 c00f6150 d8010cc0 c00f3274 d781f000 d6c84000
>> [   42.986694] 5f60: c0013020 d6e00a00 00000001 20000010 0001257c ef000000 00000000 c00895d4
>> [   42.995361] 5f80: 00000002 00000001 00000003 00000000 00000001 00000003 00000000 00000058
>> [   43.003997] 5fa0: c00130c8 c0012f00 00000001 00000003 fee1dead 28121969 01234567 00000002
>> [   43.012634] 5fc0: 00000001 00000003 00000000 00000058 00012584 0001257c 00000001 00000000
>> [   43.021270] 5fe0: 000124bc bec5cc6c 00008f9c 4a2f7c40 20000010 fee1dead 00000000 00000000
>> [   43.029968] [<c00183a4>] (smp_send_stop+0x4c/0xe4) from [<c00143d0>] (machine_restart+0xc/0x4c)
>> [   43.039154] [<c00143d0>] (machine_restart+0xc/0x4c) from [<c00511bc>] (sys_reboot+0x144/0x1f0)
>> [   43.048278] [<c00511bc>] (sys_reboot+0x144/0x1f0) from [<c0012f00>] (ret_fast_syscall+0x0/0x3c)
>> [   43.057464] Code: bad PC value
>> [   43.060760] ---[ end trace c3988d1dd0b8f0fb ]---
>> 
>> An is_smp() check is also necessary besides shilding the smp_send_stop()
>> call around CONFIG_SMP.
>> 
>> Signed-off-by: Javier Martinez Canillas <javier at dowhile0.org>
>> ---
>> arch/arm/kernel/process.c |    4 +++-
>> 1 files changed, 3 insertions(+), 1 deletions(-)
>> 
>> diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
>> index 864580a..a9043b8 100644
>> --- a/arch/arm/kernel/process.c
>> +++ b/arch/arm/kernel/process.c
>> @@ -38,6 +38,7 @@
>> #include <asm/thread_notify.h>
>> #include <asm/stacktrace.h>
>> #include <asm/mach/time.h>
>> +#include <asm/smp_plat.h>
>> 
>> #ifdef CONFIG_CC_STACKPROTECTOR
>> #include <linux/stackprotector.h>
>> @@ -240,7 +241,8 @@ __setup("reboot=", reboot_setup);
>> void machine_shutdown(void)
>> {
>> #ifdef CONFIG_SMP
>> -	smp_send_stop();
>> +	if (is_smp())
>> +		smp_send_stop();
>> #endif
>> }
>> 
>> -- 
>> 1.7.7.6
>> 
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