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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Greg KH <gregkh@linuxfoundation.org>,
	"Luis R. Rodriguez" <mcgrof@kernel.org>,
	mfuzzey@parkeon.com, "Eric W. Biederman" <ebiederm@xmission.com>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Daniel Wagner <wagi@monom.org>,
	David Woodhouse <dwmw2@infradead.org>,
	jewalt@lgsinnovations.com, rafal@milecki.pl,
	Arend Van Spriel <arend.vanspriel@broadcom.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	"Li, Yi" <yi1.li@linux.intel.com>,
	atull@kernel.org, Moritz Fischer <moritz.fischer@ettus.com>,
	Petr Mladek <pmladek@suse.com>,
	Johannes Berg <johannes.berg@intel.com>,
	Emmanuel Grumbach <emmanuel.grumbach@intel.com>,
	"Coelho, Luciano" <luciano.coelho@intel.com>,
	Kalle Valo <kvalo@codeaurora.org>,
	Andrew Lutomirski <luto@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	"AKASHI, Takahiro" <takahiro.akashi@linaro.org>,
	David Howells <dhowells@redhat.com>,
	Peter Jones <pjones@redhat.com>,
	Hans de Goede <hdegoede@redhat.com>,
	Alan Cox <alan@linux.intel.com>, "Theodore Ts'o" <tytso@mit.edu>,
	Michael Kerrisk <mtk.manpages@gmail.com>,
	Paul Gortmaker <paul.gortmaker@windriver.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Matthew Wilcox <mawilcox@microsoft.com>,
	Linux API <linux-api@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"stable # 4 . 6" <stable@vger.kernel.org>
Subject: Re: [PATCH 2/4] swait: add the missing killable swaits
Date: Thu, 29 Jun 2017 11:59:29 -0700	[thread overview]
Message-ID: <CA+55aFz8Mhx+A-g-5yOG-O1ZLRUR_fpeeA4iBNGH8EnDBZEdpA@mail.gmail.com> (raw)
In-Reply-To: <20170629183339.GD3954@linux-80c1.suse>

On Thu, Jun 29, 2017 at 11:33 AM, Davidlohr Bueso <dave@stgolabs.net> wrote:
> On Thu, 29 Jun 2017, Linus Torvalds wrote:
>
>> I actually think swait is pure garbage. Most users only wake up one
>> process anyway, and using swait for that is stupid. If you only wake
>> up one, you might as well just have a single process pointer, not a
>> wait list at all, and then use "wake_up_process()".
>
> But you still need the notion of a queue, even if you wake one task
> at a time... I'm probably missing your point here.

The *reason* they wake up only one seems to be that there really is
just one. It's some per-cpu idle thread for kvm, and for RCU it's the
RCU workqueue thread.

So the queue literally looks suspiciously pointless.

But I might be wrong, and there can actually be multiple entries. If
there are, I don't see why the wake-up-one semantics the code uses
would be valid, though.

                   Linus

  reply	other threads:[~2017-06-29 18:59 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-14 22:20 [PATCH 0/4] firmware: fix fallback mechanism by ignoring SIGCHLD Luis R. Rodriguez
2017-06-14 22:20 ` [PATCH 1/4] test_firmware: add test case for SIGCHLD on sync fallback Luis R. Rodriguez
2017-06-14 22:20 ` [PATCH 2/4] swait: add the missing killable swaits Luis R. Rodriguez
2017-06-29 12:54   ` Greg KH
2017-06-29 13:05     ` Thomas Gleixner
2017-06-29 13:35       ` Greg KH
2017-06-29 13:46         ` Thomas Gleixner
2017-06-29 16:13           ` Linus Torvalds
2017-06-29 16:31             ` Matthew Wilcox
2017-06-29 17:29               ` Luis R. Rodriguez
2017-06-29 17:40             ` Davidlohr Bueso
2017-06-29 17:57               ` Linus Torvalds
2017-06-29 18:33                 ` Davidlohr Bueso
2017-06-29 18:59                   ` Linus Torvalds [this message]
2017-06-29 19:40                     ` Luis R. Rodriguez
2017-06-29 19:44                       ` Luis R. Rodriguez
2017-06-29 20:58                         ` Jakub Kicinski
2017-06-29 22:50                           ` Luis R. Rodriguez
2017-06-29 22:53                             ` Jakub Kicinski
2017-06-29 23:00                               ` Luis R. Rodriguez
2017-06-29 23:06                                 ` Jakub Kicinski
2017-07-12 21:33                             ` Luis R. Rodriguez
2017-06-29 20:57                       ` Linus Torvalds
2017-07-05  2:06                   ` Davidlohr Bueso
2017-07-07 19:58                     ` Linus Torvalds
2017-07-07 22:27                       ` Davidlohr Bueso
2017-07-07 22:48                         ` Linus Torvalds
2017-06-29 19:15             ` Marcelo Tosatti
2017-06-30  4:03               ` Linus Torvalds
2017-06-30 11:55                 ` Marcelo Tosatti
2017-06-30 11:57                 ` Marcelo Tosatti
2017-06-30 17:30                 ` Krister Johansen
2017-06-14 22:20 ` [PATCH 3/4] firmware: avoid invalid fallback aborts by using killable swait Luis R. Rodriguez
2017-06-14 22:20 ` [PATCH 4/4] firmware: send -EINTR on signal abort on fallback mechanism Luis R. Rodriguez
2017-06-15  7:49 ` [PATCH 0/4] firmware: fix fallback mechanism by ignoring SIGCHLD Martin Fuzzey
2017-06-26 21:19 ` Luis R. Rodriguez
2017-06-29 15:14 ` Greg KH
2017-06-29 17:29   ` Luis R. Rodriguez

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