public inbox for [email protected]
 help / color / mirror / Atom feed
From: Pavel Begunkov <[email protected]>
To: Hao Xu <[email protected]>, Jens Axboe <[email protected]>
Cc: [email protected], Joseph Qi <[email protected]>
Subject: Re: [PATCH 2/2] io_uring: don't hold uring_lock when calling io_run_task_work*
Date: Wed, 3 Feb 2021 16:45:29 +0000	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 03/02/2021 16:35, Pavel Begunkov wrote:
> On 03/02/2021 14:57, Hao Xu wrote:
>> This is caused by calling io_run_task_work_sig() to do work under
>> uring_lock while the caller io_sqe_files_unregister() already held
>> uring_lock.
>> we need to check if uring_lock is held by us when doing unlock around
>> io_run_task_work_sig() since there are code paths down to that place
>> without uring_lock held.
> 
> 1. we don't want to allow parallel io_sqe_files_unregister()s
> happening, it's synchronised by uring_lock atm. Otherwise it's
> buggy.

This one should be simple, alike to

if (percpu_refs_is_dying())
	return error; // fail *files_unregister();

> 
> 2. probably same with unregister and submit.
> 
>>
>> Reported-by: Abaci <[email protected]>
>> Fixes: 1ffc54220c44 ("io_uring: fix io_sqe_files_unregister() hangs")
>> Signed-off-by: Hao Xu <[email protected]>
>> ---
>>  fs/io_uring.c | 19 +++++++++++++------
>>  1 file changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index efb6d02fea6f..b093977713ee 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -7362,18 +7362,25 @@ static int io_sqe_files_unregister(struct io_ring_ctx *ctx, bool locked)
>>  
>>  	/* wait for all refs nodes to complete */
>>  	flush_delayed_work(&ctx->file_put_work);
>> +	if (locked)
>> +		mutex_unlock(&ctx->uring_lock);
>>  	do {
>>  		ret = wait_for_completion_interruptible(&data->done);
>>  		if (!ret)
>>  			break;
>>  		ret = io_run_task_work_sig();
>> -		if (ret < 0) {
>> -			percpu_ref_resurrect(&data->refs);
>> -			reinit_completion(&data->done);
>> -			io_sqe_files_set_node(data, backup_node);
>> -			return ret;
>> -		}
>> +		if (ret < 0)
>> +			break;
>>  	} while (1);
>> +	if (locked)
>> +		mutex_lock(&ctx->uring_lock);
>> +
>> +	if (ret < 0) {
>> +		percpu_ref_resurrect(&data->refs);
>> +		reinit_completion(&data->done);
>> +		io_sqe_files_set_node(data, backup_node);
>> +		return ret;
>> +	}
>>  
>>  	__io_sqe_files_unregister(ctx);
>>  	nr_tables = DIV_ROUND_UP(ctx->nr_user_files, IORING_MAX_FILES_TABLE);
>>
> 

-- 
Pavel Begunkov

  reply	other threads:[~2021-02-03 16:50 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-03 14:57 [PATCH 0/2] fix deadlock in __io_req_task_submit() Hao Xu
2021-02-03 14:57 ` [PATCH 1/2] io_uring: add uring_lock as an argument to io_sqe_files_unregister() Hao Xu
2021-02-03 16:33   ` Pavel Begunkov
2021-02-04  3:34     ` Hao Xu
2021-02-04 11:11       ` Pavel Begunkov
2021-02-04 14:49         ` Jens Axboe
2021-02-03 14:57 ` [PATCH 2/2] io_uring: don't hold uring_lock when calling io_run_task_work* Hao Xu
2021-02-03 16:35   ` Pavel Begunkov
2021-02-03 16:45     ` Pavel Begunkov [this message]
2021-02-04  3:25       ` Hao Xu
2021-02-04 11:17         ` Pavel Begunkov
2021-02-04 15:26           ` Pavel Begunkov
2021-02-05  9:57             ` Hao Xu
2021-02-05 10:18               ` Pavel Begunkov
2021-02-06 11:34                 ` Hao Xu
2021-02-07 17:16                   ` Pavel Begunkov
2021-02-06 16:21                 ` Hao Xu
2021-02-11 13:30                 ` Hao Xu
2021-02-05 10:03       ` Hao Xu
2021-02-04 11:33   ` Pavel Begunkov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox