linux-block.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Nicolai Stange <nstange@suse.de>
To: Nicolai Stange <nstange@suse.de>
Cc: Bart Van Assche <bvanassche@acm.org>,
	Luis Chamberlain <mcgrof@kernel.org>,
	axboe@kernel.dk, viro@zeniv.linux.org.uk,
	gregkh@linuxfoundation.org, rostedt@goodmis.org,
	mingo@redhat.com, jack@suse.cz, ming.lei@redhat.com,
	mhocko@suse.com, linux-block@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Omar Sandoval <osandov@fb.com>, Hannes Reinecke <hare@suse.com>,
	Michal Hocko <mhocko@kernel.org>
Subject: Re: [RFC 3/3] block: avoid deferral of blk_release_queue() work
Date: Mon, 06 Apr 2020 11:11:01 +0200	[thread overview]
Message-ID: <87eet1j7x6.fsf@suse.de> (raw)
In-Reply-To: <87o8saj62m.fsf@suse.de> (Nicolai Stange's message of "Thu, 02 Apr 2020 16:49:37 +0200")

Nicolai Stange <nstange@suse.de> writes:

> Bart Van Assche <bvanassche@acm.org> writes:
>
>> The description of this patch mentions a single blk_release_queue() call
>> that happened in the past from a context from which sleeping is not
>> allowed and from which sleeping is allowed today. Have all other
>> blk_release_queue() / blk_put_queue() calls been verified to see whether
>> none of these happens from a context from which sleeping is not allowed?
>
> I've just done this today and found the following potentially
> problematic call paths to blk_put_queue().
>
> 1.) mem_cgroup_throttle_swaprate() takes a spinlock and
>     calls blkcg_schedule_throttle()->blk_put_queue().
>
>     Also note that AFAICS mem_cgroup_try_charge_delay() can be called
>     with GFP_ATOMIC.
>
> 2.) scsi_unblock_requests() gets called from a lot of drivers and
>     invoke blk_put_queue() through
>     scsi_unblock_requests() -> scsi_run_host_queues() ->
>     scsi_starved_list_run() -> blk_put_queue().
>
>     Most call sites are fine, the ones which are not are:
>     a.) pmcraid_complete_ioa_reset(). This gets assigned
>         to struct pmcraid_cmd's ->cmd_done and later invoked
>         under a spinlock.
>
>     b.) qla82xx_fw_dump() and qla8044_fw_dump().
>         These can potentially block w/o this patch already,
>         because both invoke qla2x00_wait_for_chip_reset().
>
> 	However, they can get called from IRQ context. For example,
>         qla82xx_intr_handler(), qla82xx_msix_default() and
>         qla82xx_poll() call qla2x00_async_event(), which calls
>         ->fw_dump().
>
> 	The aforementioned functions can also reach ->fw_dump() through
>         qla24xx_process_response_queue()->qlt_handle_abts_recv()->qlt_response_pkt_all_vps()
>         ->qlt_response_pkt()->qlt_handle_abts_completion()->qlt_chk_unresolv_exchg()
>         -> ->fw_dump().
>
> 	But I'd consider this a problem with the driver -- either
> 	->fw_dump() can sleep and must not be called from IRQ context
>         or they must not invoke qla2x00_wait_for_hba_ready().
>
>
> (I can share the full analysis, but it's lengthy and contains nothing
>  interesting except for what is listed above).
>
>
> One final note though: If I'm not mistaken, then the final
> blk_put_queue() can in principle block even today, simply by virtue of
> the kernfs operations invoked through
> kobject_put()->kobject_release()->kobject_cleanup()->kobject_del()
> ->sysfs_remove_dir()->kernfs_remove()->mutex_lock()?\

That's wrong, I missed kobject_del() invocation issued from
blk_unregister_queue(). Thus, blk_put_queue() in its current
implementation won't ever block.

Thanks,

Nicolai

-- 
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg), GF: Felix Imendörffer

  reply	other threads:[~2020-04-06  9:11 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-01 23:59 [RFC 0/3] block: address blktrace use-after-free Luis Chamberlain
2020-04-02  0:00 ` [RFC 1/3] block: move main block debugfs initialization to its own file Luis Chamberlain
2020-04-05  3:12   ` Bart Van Assche
2020-04-06 14:23     ` Luis Chamberlain
2020-04-02  0:00 ` [RFC 2/3] blktrace: fix debugfs use after free Luis Chamberlain
2020-04-02  1:57   ` Eric Sandeen
2020-04-02 16:14     ` Luis Chamberlain
2020-04-05  3:39   ` Bart Van Assche
2020-04-06  1:27     ` Eric Sandeen
2020-04-06  4:25       ` Bart Van Assche
2020-04-06  9:18         ` Nicolai Stange
2020-04-06 15:19           ` Luis Chamberlain
2020-04-07  8:15             ` Luis Chamberlain
2020-04-06 14:29         ` Eric Sandeen
2020-04-07  8:09           ` Luis Chamberlain
2020-04-06 15:14     ` Luis Chamberlain
2020-04-02  0:00 ` [RFC 3/3] block: avoid deferral of blk_release_queue() work Luis Chamberlain
2020-04-02  3:39   ` Bart Van Assche
2020-04-02 14:49     ` Nicolai Stange
2020-04-06  9:11       ` Nicolai Stange [this message]
2020-04-09 18:11       ` Luis Chamberlain
2020-04-02  7:44 ` [RFC 0/3] block: address blktrace use-after-free Greg KH
2020-04-03  8:19 ` Ming Lei
2020-04-03 14:06   ` Luis Chamberlain
2020-04-03 14:13   ` Bart Van Assche
2020-04-03 19:49     ` Luis Chamberlain
2020-04-07  2:47   ` yukuai (C)
2020-04-07 19:00     ` Luis Chamberlain
2020-04-09 20:59       ` Luis Chamberlain

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 \
    --in-reply-to=87eet1j7x6.fsf@suse.de \
    --to=nstange@suse.de \
    --cc=axboe@kernel.dk \
    --cc=bvanassche@acm.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=hare@suse.com \
    --cc=jack@suse.cz \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mcgrof@kernel.org \
    --cc=mhocko@kernel.org \
    --cc=mhocko@suse.com \
    --cc=ming.lei@redhat.com \
    --cc=mingo@redhat.com \
    --cc=osandov@fb.com \
    --cc=rostedt@goodmis.org \
    --cc=viro@zeniv.linux.org.uk \
    --subject='Re: [RFC 3/3] block: avoid deferral of blk_release_queue() work' \
    /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

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox