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From: Jessica Yu <jeyu@redhat.com>
To: Petr Mladek <pmladek@suse.com>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Kees Cook <keescook@chromium.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Shuah Khan <shuah@kernel.org>,
	Rusty Russell <rusty@rustcorp.com.au>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Arnaldo Carvalho de Melo <acme@redhat.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Josh Triplett <josh@joshtriplett.org>,
	martin.wilck@suse.com, Michal Marek <mmarek@suse.com>,
	hare <hare@suse.com>,
	rwright@hpe.com, Jeff Mahoney <jeffm@suse.com>,
	David Sterba <DSterba@suse.com>,
	Filipe Manana <fdmanana@suse.com>, NeilBrown <neilb@suse.com>,
	Guenter Roeck <linux@roeck-us.net>,
	rgoldwyn@suse.com,
	Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>,
	Heinrich Schuchardt <xypron.glpk@gmx.de>,
	Aaron Tomlin <atomlin@redhat.com>,
	Miroslav Benes <mbenes@suse.cz>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	"David S. Miller" <davem@davemloft.net>,
	Ingo Molnar <mingo@redhat.com>, Alan Cox <alan@linux.intel.com>,
	"Ted Ts'o" <tytso@mit.edu>, Greg KH <gregkh@linuxfoundation.org>,
	linux-kselftest@vger.kernel.org,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 0/4] kmod: help make deterministic
Date: Tue, 27 Jun 2017 12:04:03 +0200
Message-ID: <20170627100402.mjlrp2oy6x6opco5@redbean> (raw)
In-Reply-To: <20170627081339.GC7071@pathway.suse.cz>

+++ Petr Mladek [27/06/17 10:13 +0200]:
>On Tue 2017-06-27 02:27:44, Luis R. Rodriguez wrote:
>> On Tue, Jun 27, 2017 at 12:44:42AM +0200, Luis R. Rodriguez wrote:
>> > On Mon, Jun 26, 2017 at 11:37:36PM +0200, Jessica Yu wrote:
>> > > +++ Kees Cook [20/06/17 17:23 -0700]:
>> > > > On Tue, Jun 20, 2017 at 1:56 PM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
>> > > > > On Fri, May 26, 2017 at 02:12:24PM -0700, Luis R. Rodriguez wrote:
>> > > > > > Luis R. Rodriguez (4):
>> > > > > >   module: use list_for_each_entry_rcu() on find_module_all()
>> > > > > >   kmod: reduce atomic operations on kmod_concurrent and simplify
>> > > > > >   kmod: add test driver to stress test the module loader
>> > > > > >   kmod: throttle kmod thread limit
>> > > > >
>> > > > > About a month now with no further nitpicks. What tree should these changes
>> > > > > go through if there are no issues? Andrew's, Jessica's ?
>> > > >
>> > > > Seems like going through Jessica's would make the most sense?
>> > >
>> > > Would be happy to take patches 01 (which I need to anyway), 02,
>> > > possibly 04 if decoupled from the test driver (03).
>> >
>> > Feel free to decouple it, but note that then the commit log must then be
>> > changed. My own take is this fix is not so critical as it is a corner case, so
>> > I have instead preferred to couple in the test case and respective fix
>> > together. I'll leave it up to you how to proceed.
>>
>> Note: Linus noted swait is actually very special use-case [0] so I'd hate to
>> add a new use case not vetted for. This use case on kmod.c really does *not*
>> require anything but a simple wait though, so really am inclined to let that
>> through unless I hear back...
>>
>> [0] https://lkml.kernel.org/r/20170627001534.GK21846@wotan.suse.de
>
>Heh, I was not aware of this special case either. The welcoming
>comment of the swait API confused me as well.
>
>In this light, I suggest to switch the patch to using the normal wait API.

Huh, I wasn't aware either :-/ But I agree, judging from Linus'
response [0], it's probably best to use the well established wait_*
variants. I'm not sure I understood why the patch switched to swait,
but in any case I don't think we'd be hitting the "thundering herd"
problem very often here (and if we do, we could just use exclusive
wait. But in that scenario I'd be more interested in why a normal
system would be battered with more than 50 in-kernel modprobe requests
at a time).

[0] https://marc.info/?l=linux-kernel&m=149851347228696&w=2

  reply index

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-19  3:24 [PATCH 0/6] kmod: few simple enhancements Luis R. Rodriguez
2017-05-19  3:24 ` [PATCH 1/6] kmod: add dynamic max concurrent thread count Luis R. Rodriguez
2017-05-19 20:44   ` Dmitry Torokhov
     [not found]     ` <CAB=NE6XGL24O+JfTNUG0HO4obhDc-v+HyL0SCrQELiZrj2-qNw@mail.gmail.com>
     [not found]       ` <CAB=NE6Wa4Nemh80yaCCwbjrNRLPD+GJMncg12APg9Vq63AWVng@mail.gmail.com>
     [not found]         ` <CAB=NE6Vc6RDAytn2Pkv2V58HFo8ncR0eOHZ3===kbZ2NF78ubg@mail.gmail.com>
     [not found]           ` <CAB=NE6Vqmx=y6muenpuQKynTP=pGWMF8tzoCA0BXD6d63q9wPg@mail.gmail.com>
2017-05-19 21:58             ` Dmitry Torokhov
2017-05-25 16:22               ` Luis R. Rodriguez
2017-05-25 16:38                 ` Dmitry Torokhov
2017-05-25 16:50                   ` Luis R. Rodriguez
2017-05-25 17:30                     ` Dmitry Torokhov
2017-05-25 17:38                       ` Luis R. Rodriguez
2017-05-25 18:06                         ` Luis R. Rodriguez
2017-05-25 18:26                           ` Dmitry Torokhov
2017-05-25 19:01                             ` Luis R. Rodriguez
2017-05-25 21:38                               ` Luis R. Rodriguez
2017-05-19  3:24 ` [PATCH 2/6] module: use list_for_each_entry_rcu() on find_module_all() Luis R. Rodriguez
2017-05-23 14:46   ` Miroslav Benes
2017-05-19  3:24 ` [PATCH 3/6] kmod: provide wrappers for kmod_concurrent inc/dec Luis R. Rodriguez
2017-05-19  3:24 ` [PATCH 4/6] kmod: return -EBUSY if modprobe limit is reached Luis R. Rodriguez
2017-05-19  3:24 ` [PATCH 5/6] kmod: preempt on kmod_umh_threads_get() Luis R. Rodriguez
2017-05-19 22:27   ` Dmitry Torokhov
2017-05-25  0:14     ` Luis R. Rodriguez
2017-05-25  0:45       ` Dmitry Torokhov
2017-05-25  1:00         ` Luis R. Rodriguez
2017-05-25  2:27           ` Dmitry Torokhov
2017-05-25 11:19             ` Petr Mladek
2017-05-25 15:38               ` Luis R. Rodriguez
2017-05-25 16:42               ` Dmitry Torokhov
2017-05-25 15:18             ` Jessica Yu
2017-05-19  3:24 ` [PATCH 6/6] kmod: use simplified rate limit printk Luis R. Rodriguez
2017-05-19 22:23   ` Dmitry Torokhov
2017-05-23  9:00     ` Petr Mladek
2017-05-26  0:16 ` [PATCH v2 0/5] kmod: help make deterministic Luis R. Rodriguez
2017-05-26  0:16   ` [PATCH v2 1/5] module: use list_for_each_entry_rcu() on find_module_all() Luis R. Rodriguez
2017-05-26  0:16   ` [PATCH v2 2/5] kmod: reduce atomic operations on kmod_concurrent Luis R. Rodriguez
2017-05-26  1:11     ` Dmitry Torokhov
2017-05-26 20:03       ` Luis R. Rodriguez
2017-05-26  0:16   ` [PATCH v2 3/5] kmod: add test driver to stress test the module loader Luis R. Rodriguez
2017-05-26  0:16   ` [PATCH v2 4/5] kmod: add helpers for getting kmod limit Luis R. Rodriguez
2017-05-26  0:56     ` Dmitry Torokhov
2017-05-26 20:27       ` Luis R. Rodriguez
2017-05-26  0:16   ` [PATCH v2 5/5] kmod: throttle kmod thread limit Luis R. Rodriguez
2017-05-26 21:12   ` [PATCH v3 0/4] kmod: help make deterministic Luis R. Rodriguez
2017-05-26 21:12     ` [PATCH v3 1/4] module: use list_for_each_entry_rcu() on find_module_all() Luis R. Rodriguez
2017-05-26 21:12     ` [PATCH v3 2/4] kmod: reduce atomic operations on kmod_concurrent and simplify Luis R. Rodriguez
2017-06-23 19:19       ` [PATCH v4 " Luis R. Rodriguez
2017-06-26 11:36       ` [PATCH v3 " Petr Mladek
2017-05-26 21:12     ` [PATCH v3 3/4] kmod: add test driver to stress test the module loader Luis R. Rodriguez
2017-05-26 21:12     ` [PATCH v3 4/4] kmod: throttle kmod thread limit Luis R. Rodriguez
2017-06-22 15:19       ` Petr Mladek
2017-06-23 16:16         ` Luis R. Rodriguez
2017-06-23 17:56           ` Luis R. Rodriguez
2017-06-23 19:16             ` Luis R. Rodriguez
2017-06-26 10:03               ` Petr Mladek
2017-06-26  9:55           ` Petr Mladek
2017-06-23 19:20       ` [PATCH v4 " Luis R. Rodriguez
2017-06-26 11:38         ` Petr Mladek
2017-06-28 22:11           ` Luis R. Rodriguez
2017-06-20 20:56     ` [PATCH v3 0/4] kmod: help make deterministic Luis R. Rodriguez
2017-06-21  0:23       ` Kees Cook
2017-06-26 21:37         ` Jessica Yu
2017-06-26 22:44           ` Luis R. Rodriguez
2017-06-27  0:27             ` Luis R. Rodriguez
2017-06-27  8:13               ` Petr Mladek
2017-06-27 10:04                 ` Jessica Yu [this message]
2017-06-27 15:26             ` Jessica Yu
2017-06-28  0:49               ` Luis R. Rodriguez
2017-06-28 22:31     ` [PATCH v4 0/3] " Luis R. Rodriguez
2017-06-28 22:31       ` [PATCH v4 1/3] MAINTAINERS: give kmod some maintainer love Luis R. Rodriguez
2017-06-28 22:31       ` [PATCH v4 2/3] kmod: add test driver to stress test the module loader Luis R. Rodriguez
2017-06-28 22:31       ` [PATCH v4 3/3] kmod: throttle kmod thread limit Luis R. Rodriguez

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