From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org,
dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com,
fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com
Subject: Re: [PATCH tip/core/rcu 09/12] rcu: Make call_rcu_tasks() tolerate first call with irqs disabled
Date: Wed, 15 Jun 2016 15:58:13 -0700 [thread overview]
Message-ID: <20160615225813.GC3923@linux.vnet.ibm.com> (raw)
In-Reply-To: <20160615221604.GC30921@twins.programming.kicks-ass.net>
On Thu, Jun 16, 2016 at 12:16:04AM +0200, Peter Zijlstra wrote:
> On Wed, Jun 15, 2016 at 02:46:10PM -0700, Paul E. McKenney wrote:
> > Currently, if the very first call to call_rcu_tasks() has irqs disabled,
> > it will create the rcu_tasks_kthread with irqs disabled, which will
> > result in a splat in the memory allocator, which kthread_run() invokes
> > with the expectation that irqs are enabled.
> >
> > This commit fixes this problem by deferring kthread creation if called
> > with irqs disabled. The first call to call_rcu_tasks() that has irqs
> > enabled will create the kthread.
> >
> > This bug was detected by rcutorture changes that were motivated by
> > Iftekhar Ahmed's mutation-testing efforts.
>
> Seems fragile. What if someone manages to only use call_rcu_tasks() with
> IRQs disabled?
It would have to have users before that could possibly happen. :-/
And it would not be hard to remove the fragility if needed by setting
up a workqueue, possibly mediated by a timer or whatever. But it is
hard to motivate myself to do so in advance of users. For that matter...
Steven, is call_rcu_tasks() needed, or should I just rip it out?
Thanx, Paul
next prev parent reply other threads:[~2016-06-15 22:58 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-15 21:45 [PATCH tip/core/rcu 0/12] Miscellaneous RCU fixes for 4.8 Paul E. McKenney
2016-06-15 21:46 ` [PATCH tip/core/rcu 01/12] rcu: Fix outdated rcu_scheduler_active comment Paul E. McKenney
2016-06-15 21:46 ` [PATCH tip/core/rcu 02/12] rcu: Fix outdated hotplug-exclusion comment in rcu_gp_init() Paul E. McKenney
2016-06-15 21:46 ` [PATCH tip/core/rcu 03/12] rcu: Remove some superfluous lines Paul E. McKenney
2016-06-15 21:46 ` [PATCH tip/core/rcu 04/12] rcu: Move expedited code from tree.c to tree_exp.h Paul E. McKenney
2016-06-15 22:05 ` Peter Zijlstra
2016-06-15 22:16 ` Paul E. McKenney
2016-06-17 15:48 ` Pranith Kumar
2016-06-17 17:46 ` Paul E. McKenney
2016-06-15 21:46 ` [PATCH tip/core/rcu 05/12] rcu: Move expedited code from tree_plugin.h " Paul E. McKenney
2016-06-15 21:46 ` [PATCH tip/core/rcu 06/12] rcu: Document RCU_NONIDLE() restrictions in comment header Paul E. McKenney
2016-06-15 21:46 ` [PATCH tip/core/rcu 07/12] rcu: No ordering for rcu_assign_pointer() of NULL Paul E. McKenney
2016-06-15 22:03 ` Peter Zijlstra
2016-06-15 22:12 ` Peter Zijlstra
2016-06-15 22:41 ` Paul E. McKenney
2016-06-15 21:46 ` [PATCH tip/core/rcu 08/12] rcu: Disable TASKS_RCU for usermode Linux Paul E. McKenney
2016-06-15 21:47 ` Richard Weinberger
2016-06-15 21:46 ` [PATCH tip/core/rcu 09/12] rcu: Make call_rcu_tasks() tolerate first call with irqs disabled Paul E. McKenney
2016-06-15 22:15 ` Peter Zijlstra
2016-06-15 22:54 ` Paul E. McKenney
2016-06-15 22:16 ` Peter Zijlstra
2016-06-15 22:58 ` Paul E. McKenney [this message]
2016-06-15 21:46 ` [PATCH tip/core/rcu 10/12] rcu: Fix a typo in a comment Paul E. McKenney
2016-06-15 21:46 ` [PATCH tip/core/rcu 11/12] rcu: sysctl: Panic on RCU Stall Paul E. McKenney
2016-06-15 21:46 ` [PATCH tip/core/rcu 12/12] rcu: Correctly handle sparse possible cpus Paul E. McKenney
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=20160615225813.GC3923@linux.vnet.ibm.com \
--to=paulmck@linux.vnet.ibm.com \
--cc=akpm@linux-foundation.org \
--cc=bobby.prani@gmail.com \
--cc=dhowells@redhat.com \
--cc=dipankar@in.ibm.com \
--cc=dvhart@linux.intel.com \
--cc=edumazet@google.com \
--cc=fweisbec@gmail.com \
--cc=jiangshanlai@gmail.com \
--cc=josh@joshtriplett.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.