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From: Jens Axboe <[email protected]>
To: "Eric W. Biederman" <[email protected]>
Cc: [email protected], [email protected],
	[email protected], [email protected], [email protected]
Subject: Re: [PATCH 1/7] kernel: don't call do_exit() for PF_IO_WORKER threads
Date: Fri, 26 Mar 2021 16:11:18 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 3/26/21 2:43 PM, Eric W. Biederman wrote:
> Jens Axboe <[email protected]> writes:
> 
>> Right now we're never calling get_signal() from PF_IO_WORKER threads, but
>> in preparation for doing so, don't handle a fatal signal for them. The
>> workers have state they need to cleanup when exiting, and they don't do
>> coredumps, so just return instead of performing either a dump or calling
>> do_exit() on their behalf. The threads themselves will detect a fatal
>> signal and do proper shutdown.
>>
>> Signed-off-by: Jens Axboe <[email protected]>
>> ---
>>  kernel/signal.c | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>>
>> diff --git a/kernel/signal.c b/kernel/signal.c
>> index f2a1b898da29..e3e1b8fbfe8a 100644
>> --- a/kernel/signal.c
>> +++ b/kernel/signal.c
>> @@ -2756,6 +2756,15 @@ bool get_signal(struct ksignal *ksig)
>>  		 */
>>  		current->flags |= PF_SIGNALED;
>>  
>> +		/*
>> +		 * PF_IO_WORKER threads will catch and exit on fatal signals
>> +		 * themselves. They have cleanup that must be performed, so
>> +		 * we cannot call do_exit() on their behalf. coredumps also
>> +		 * do not apply to them.
>> +		 */
>> +		if (current->flags & PF_IO_WORKER)
>> +			return false;
>> +
> 
> Returning false when get_signal needs the caller to handle a signal
> adds a very weird and awkward special case to how get_signal returns
> arguments.
> 
> Instead you should simply break and let get_signal return SIGKILL like
> any other signal that has a handler that the caller of get_signal needs
> to handle.
> 
> Something like:
>> +		/*
>> +		 * PF_IO_WORKER have cleanup that must be performed,
>> +		 * before calling do_exit().
>> +		 */
>> +		if (current->flags & PF_IO_WORKER)
>> +			break;
> 
> 
> As do_coredump does not call do_exit there is no reason to skip calling into
> the coredump handling either.   And allowing it will remove yet another
> special case from the io worker code.

Thanks, I'll turn it into a break, that does seem like a better idea in
general. Actually it wants to be a goto or similar, as a break will
assume that we have the sighand lock held. With the coredump being
irrelevant, I'll just it before the do_exit() call.

-- 
Jens Axboe


  reply	other threads:[~2021-03-26 22:12 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-26 15:51 [PATCHSET v2 0/7] Allow signals for IO threads Jens Axboe
2021-03-26 15:51 ` [PATCH 1/7] kernel: don't call do_exit() for PF_IO_WORKER threads Jens Axboe
2021-03-26 20:43   ` Eric W. Biederman
2021-03-26 22:11     ` Jens Axboe [this message]
2021-03-26 15:51 ` [PATCH 2/7] io_uring: handle signals for IO threads like a normal thread Jens Axboe
2021-03-26 20:29   ` Eric W. Biederman
2021-03-26 22:14     ` Jens Axboe
2021-03-26 22:23       ` Eric W. Biederman
2021-03-26 22:30         ` Jens Axboe
2021-03-26 22:35           ` Eric W. Biederman
2021-03-26 22:38             ` Jens Axboe
2021-03-26 22:49               ` Jens Axboe
2021-03-27 17:40                 ` Eric W. Biederman
2021-03-27 20:08                   ` Jens Axboe
2021-03-26 15:51 ` [PATCH 03/10] Revert "signal: don't allow sending any signals to PF_IO_WORKER threads" Jens Axboe
2021-03-26 15:51 ` [PATCH 3/7] kernel: stop masking signals in create_io_thread() Jens Axboe
2021-03-26 20:44   ` Eric W. Biederman
2021-03-26 15:51 ` [PATCH 04/10] Revert "kernel: treat PF_IO_WORKER like PF_KTHREAD for ptrace/signals" Jens Axboe
2021-03-26 15:51 ` [PATCH 4/7] Revert "signal: don't allow sending any signals to PF_IO_WORKER threads" Jens Axboe
2021-03-26 15:51 ` [PATCH 05/10] Revert "kernel: freezer should treat PF_IO_WORKER like PF_KTHREAD for freezing" Jens Axboe
2021-03-26 15:51 ` [PATCH 5/7] Revert "kernel: treat PF_IO_WORKER like PF_KTHREAD for ptrace/signals" Jens Axboe
2021-03-26 15:51 ` [PATCH 6/7] Revert "kernel: freezer should treat PF_IO_WORKER like PF_KTHREAD for freezing" Jens Axboe
2021-03-26 15:51 ` [PATCH 06/10] Revert "signal: don't allow STOP on PF_IO_WORKER threads" Jens Axboe
2021-03-26 15:51 ` [PATCH 7/7] " Jens Axboe
2021-03-26 15:51 ` [PATCH 07/10] io_uring: fix timeout cancel return code Jens Axboe
2021-03-26 15:51 ` [PATCH 08/10] io_uring: do post-completion chore on t-out cancel Jens Axboe
2021-03-26 15:51 ` [PATCH 09/10] io_uring: don't cancel-track common timeouts Jens Axboe
2021-03-26 15:51 ` [PATCH 10/10] io_uring: don't cancel extra on files match Jens Axboe
2021-03-26 15:54 ` [PATCHSET v2 0/7] Allow signals for IO threads Jens Axboe

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