* Question: Can I call down() in an atomic context?
@ 2021-08-06 2:35 Xiaoming Ni
2021-08-06 8:23 ` Peter Zijlstra
0 siblings, 1 reply; 2+ messages in thread
From: Xiaoming Ni @ 2021-08-06 2:35 UTC (permalink / raw)
To: Peter Zijlstra, mingo, Will Deacon, longman, boqun.feng,
Linux Kernel Mailing List, Matthew Wilcox, rjw, lenb, Hanjun Guo,
xiaoqian9, wangle6
might_sleep() is called in kernel/locking/rwsem.c (API:
down_read/down_write/...)
but not in kernel/locking/semaphore.c (API: down/down_timeout/..).
Was it designed so purposely, or was it missed by mistake?
After I added might_sleep() to kernel/locking/semaphore.c,
an alarm log was occasionally detected in my test environment:
BUG: sleeping function called from invalid context at
kernel/locking/semaphore.c:163
in_atomic(): 1, irqs_disabled(): 128, pid: 0, name: swapper/8
...
Call trace:
dump_backtrace+0x0/0x3c
dump_backtrace+0x2c/0x3c
show_stack+0x24/0x34
dump_stack+0xb0/0xf0
___might_sleep+0x130/0x144
__might_sleep+0x78/0x88
down_timeout+0x40/0xc8
acpi_os_wait_semaphore+0x78/0xa0 drivers/acpi/osl.c#L1266
acpi_ut_acquire_mutex+0x50/0xb4 drivers/acpi/acpica/utmutex.c#L241
acpi_get_table+0x3c/0xc8 drivers/acpi/acpica/tbxface.c#L318
acpi_find_last_cache_level+0x7c/0x140 drivers/acpi/pptt.c#L602
_init_cache_level+0xd0/0xd8 arch/arm64/kernel/cacheinfo.c#L64
flush_smp_call_function_queue+0x138/0x160 kernel/smp.c#L561
generic_smp_call_function_single_interrupt+0x18/0x24
handle_IPI+0x1d0/0x50c
gic_handle_irq+0x13c/0x140
el1_irq+0xcc/0x180
arch_cpu_idle+0xc0/0x16c
default_idle_call+0x34/0x38
cpu_startup_entry+0x2b4/0x358
secondary_start_kernel+0x1a8/0x1dc
Does this mean that it is necessary to add might_sleep in
kernel/locking/semaphore.c?
Thanks
Xiaoming Ni
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Question: Can I call down() in an atomic context?
2021-08-06 2:35 Question: Can I call down() in an atomic context? Xiaoming Ni
@ 2021-08-06 8:23 ` Peter Zijlstra
0 siblings, 0 replies; 2+ messages in thread
From: Peter Zijlstra @ 2021-08-06 8:23 UTC (permalink / raw)
To: Xiaoming Ni
Cc: mingo, Will Deacon, longman, boqun.feng,
Linux Kernel Mailing List, Matthew Wilcox, rjw, lenb, Hanjun Guo,
xiaoqian9, wangle6
On Fri, Aug 06, 2021 at 10:35:36AM +0800, Xiaoming Ni wrote:
> might_sleep() is called in kernel/locking/rwsem.c (API:
> down_read/down_write/...)
> but not in kernel/locking/semaphore.c (API: down/down_timeout/..).
> Was it designed so purposely, or was it missed by mistake?
Simply forgotten I suspect. The semaphore is definitely a sleeping lock.
> After I added might_sleep() to kernel/locking/semaphore.c,
> an alarm log was occasionally detected in my test environment:
>
> BUG: sleeping function called from invalid context at
> kernel/locking/semaphore.c:163
> in_atomic(): 1, irqs_disabled(): 128, pid: 0, name: swapper/8
> ...
> Call trace:
> dump_backtrace+0x0/0x3c
> dump_backtrace+0x2c/0x3c
> show_stack+0x24/0x34
> dump_stack+0xb0/0xf0
> ___might_sleep+0x130/0x144
> __might_sleep+0x78/0x88
> down_timeout+0x40/0xc8
> acpi_os_wait_semaphore+0x78/0xa0 drivers/acpi/osl.c#L1266
> acpi_ut_acquire_mutex+0x50/0xb4 drivers/acpi/acpica/utmutex.c#L241
> acpi_get_table+0x3c/0xc8 drivers/acpi/acpica/tbxface.c#L318
> acpi_find_last_cache_level+0x7c/0x140 drivers/acpi/pptt.c#L602
> _init_cache_level+0xd0/0xd8 arch/arm64/kernel/cacheinfo.c#L64
> flush_smp_call_function_queue+0x138/0x160 kernel/smp.c#L561
> generic_smp_call_function_single_interrupt+0x18/0x24
> handle_IPI+0x1d0/0x50c
> gic_handle_irq+0x13c/0x140
> el1_irq+0xcc/0x180
> arch_cpu_idle+0xc0/0x16c
> default_idle_call+0x34/0x38
> cpu_startup_entry+0x2b4/0x358
> secondary_start_kernel+0x1a8/0x1dc
>
> Does this mean that it is necessary to add might_sleep in
> kernel/locking/semaphore.c?
Necessary might be the wrong word, but yes, I think the whole down_*()
family (with exception of down_trylock() obvs) could do with a
might_sleep().
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-08-06 2:35 Question: Can I call down() in an atomic context? Xiaoming Ni
2021-08-06 8:23 ` Peter Zijlstra
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