From: Peter Zijlstra <peterz@infradead.org>
To: Xiaoming Ni <nixiaoming@huawei.com>
Cc: mingo@redhat.com, Will Deacon <will@kernel.org>,
longman@redhat.com, boqun.feng@gmail.com,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Matthew Wilcox <willy@infradead.org>,
rjw@rjwysocki.net, lenb@kernel.org,
Hanjun Guo <guohanjun@huawei.com>,
"xiaoqian9@huawei.com" <xiaoqian9@huawei.com>,
"wangle6@huawei.com" <wangle6@huawei.com>
Subject: Re: Question: Can I call down() in an atomic context?
Date: Fri, 6 Aug 2021 10:23:20 +0200 [thread overview]
Message-ID: <20210806082320.GD22037@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <6b5e1da8-4360-e9da-ad42-a5365fb853fa@huawei.com>
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().
prev parent reply other threads:[~2021-08-06 8:28 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-06 2:35 Question: Can I call down() in an atomic context? Xiaoming Ni
2021-08-06 8:23 ` Peter Zijlstra [this message]
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