From: Oleg Nesterov <oleg@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
tj@kernel.org, tglx@linutronix.de, peterz@infradead.org,
paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au,
mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org,
vincent.guittot@linaro.org, sbw@mit.edu,
amit.kucheria@linaro.org, rjw@sisk.pl,
wangyun@linux.vnet.ibm.com, xiaoguangrong@linux.vnet.ibm.com,
nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2 01/10] CPU hotplug: Provide APIs for "light" atomic readers to prevent CPU offline
Date: Mon, 10 Dec 2012 19:21:15 +0100 [thread overview]
Message-ID: <20121210182115.GA30892@redhat.com> (raw)
In-Reply-To: <20121207200014.GB13238@redhat.com>
On 12/07, Oleg Nesterov wrote:
>
> On 12/06, Steven Rostedt wrote:
> >
> > You know reader locks can deadlock with each other, right? And this
> > isn't caught be lockdep yet. This is because rwlocks have been made to
> > be fair with writers. Before writers could be starved if a CPU always
> > let a reader in. Now if a writer is waiting, a reader will block behind
> > the writer. But this has introduced new issues with the kernel as
> > follows:
> >
> >
> > CPU0 CPU1 CPU2 CPU3
> > ---- ---- ---- ----
> > read_lock(A);
> > read_lock(B)
> > write_lock(A) <- block
> > write_lock(B) <- block
> > read_lock(B) <-block
> >
> > read_lock(A) <- block
> >
> > DEADLOCK!
>
> Really??? Oh I didn't know...
>
> Yes this was always true for rwsem, but rwlock_t?
Sorry, please ignore my email. I misread your email.
Oleg.
next prev parent reply other threads:[~2012-12-10 18:21 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-05 18:42 [RFC PATCH v2 00/10][RESEND] CPU hotplug: stop_machine()-free CPU hotplug Srivatsa S. Bhat
2012-12-05 18:43 ` [RFC PATCH v2 01/10] CPU hotplug: Provide APIs for "light" atomic readers to prevent CPU offline Srivatsa S. Bhat
2012-12-05 18:47 ` Srivatsa S. Bhat
2012-12-05 18:51 ` Srivatsa S. Bhat
2012-12-05 18:53 ` Srivatsa S. Bhat
2012-12-05 18:56 ` Srivatsa S. Bhat
2012-12-05 18:59 ` Srivatsa S. Bhat
2012-12-05 20:14 ` Srivatsa S. Bhat
2012-12-06 16:18 ` Oleg Nesterov
2012-12-06 18:48 ` Srivatsa S. Bhat
2012-12-06 19:17 ` Srivatsa S. Bhat
2012-12-07 21:01 ` Oleg Nesterov
2012-12-06 19:28 ` Steven Rostedt
2012-12-06 19:36 ` Srivatsa S. Bhat
2012-12-06 22:02 ` Steven Rostedt
2012-12-07 17:33 ` Srivatsa S. Bhat
[not found] ` <20121207200014.GB13238@redhat.com>
2012-12-10 18:21 ` Oleg Nesterov [this message]
2012-12-10 19:07 ` Steven Rostedt
2012-12-07 19:56 ` Oleg Nesterov
2012-12-07 20:25 ` Srivatsa S. Bhat
2012-12-07 20:59 ` Oleg Nesterov
2012-12-05 19:07 ` Oleg Nesterov
2012-12-05 19:16 ` Srivatsa S. Bhat
2012-12-05 18:43 ` [RFC PATCH v2 02/10] CPU hotplug: Provide APIs for "full" " Srivatsa S. Bhat
2012-12-05 19:01 ` Srivatsa S. Bhat
2012-12-05 20:31 ` Srivatsa S. Bhat
2012-12-05 20:57 ` Tejun Heo
2012-12-06 4:31 ` Srivatsa S. Bhat
2012-12-05 18:43 ` [RFC PATCH v2 03/10] CPU hotplug: Convert preprocessor macros to static inline functions Srivatsa S. Bhat
2012-12-05 18:43 ` [RFC PATCH v2 04/10] smp, cpu hotplug: Fix smp_call_function_*() to prevent CPU offline properly Srivatsa S. Bhat
2012-12-05 18:43 ` [RFC PATCH v2 05/10] smp, cpu hotplug: Fix on_each_cpu_*() " Srivatsa S. Bhat
2012-12-05 18:44 ` [RFC PATCH v2 06/10] sched, cpu hotplug: Use stable online cpus in try_to_wake_up() & select_task_rq() Srivatsa S. Bhat
2012-12-05 18:44 ` [RFC PATCH v2 07/10] kick_process(), cpu-hotplug: Prevent offlining of target CPU properly Srivatsa S. Bhat
2012-12-05 18:44 ` [RFC PATCH v2 08/10] yield_to(), cpu-hotplug: Prevent offlining of other CPUs properly Srivatsa S. Bhat
2012-12-05 18:44 ` [RFC PATCH v2 09/10] kvm, vmx: Add full atomic synchronization with CPU Hotplug Srivatsa S. Bhat
2012-12-05 18:45 ` [RFC PATCH v2 10/10] cpu: No more __stop_machine() in _cpu_down() Srivatsa S. Bhat
2012-12-05 19:08 ` Oleg Nesterov
2012-12-05 19:12 ` Srivatsa S. Bhat
[not found] <20121205131038.17383.55472.stgit@srivatsabhat.in.ibm.com>
[not found] ` <20121205131136.17383.23318.stgit@srivatsabhat.in.ibm.com>
[not found] ` <20121205142316.GI3885@mtj.dyndns.org>
[not found] ` <20121205164640.GA7382@redhat.com>
[not found] ` <20121205165356.GL3885@mtj.dyndns.org>
2012-12-05 18:32 ` [RFC PATCH v2 01/10] CPU hotplug: Provide APIs for "light" atomic readers to prevent CPU offline Srivatsa S. Bhat
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=20121210182115.GA30892@redhat.com \
--to=oleg@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=amit.kucheria@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=namhyung@kernel.org \
--cc=nikunj@linux.vnet.ibm.com \
--cc=paulmck@linux.vnet.ibm.com \
--cc=peterz@infradead.org \
--cc=rjw@sisk.pl \
--cc=rostedt@goodmis.org \
--cc=rusty@rustcorp.com.au \
--cc=sbw@mit.edu \
--cc=srivatsa.bhat@linux.vnet.ibm.com \
--cc=tglx@linutronix.de \
--cc=tj@kernel.org \
--cc=vincent.guittot@linaro.org \
--cc=wangyun@linux.vnet.ibm.com \
--cc=xiaoguangrong@linux.vnet.ibm.com \
/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;
as well as URLs for NNTP newsgroup(s).