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 07/13] rcu: Move preemption disabling out of __srcu_read_lock()
Date: Tue, 6 Oct 2015 14:03:48 -0700 [thread overview]
Message-ID: <20151006210348.GY3910@linux.vnet.ibm.com> (raw)
In-Reply-To: <20151006203224.GY3604@twins.programming.kicks-ass.net>
On Tue, Oct 06, 2015 at 10:32:24PM +0200, Peter Zijlstra wrote:
> On Tue, Oct 06, 2015 at 01:19:15PM -0700, Paul E. McKenney wrote:
> > On Tue, Oct 06, 2015 at 10:07:25PM +0200, Peter Zijlstra wrote:
> > > On Tue, Oct 06, 2015 at 09:13:42AM -0700, Paul E. McKenney wrote:
> > > > Currently, __srcu_read_lock() cannot be invoked from restricted
> > > > environments because it contains calls to preempt_disable() and
> > > > preempt_enable(), both of which can invoke lockdep, which is a bad
> > > > idea in some restricted execution modes. This commit therefore moves
> > > > the preempt_disable() and preempt_enable() from __srcu_read_lock()
> > > > to srcu_read_lock(). It also inserts the preempt_disable() and
> > > > preempt_enable() around the call to __srcu_read_lock() in do_exit().
> > >
> > > Did you not simply want to use: preempt_disable_notrace() ?
> >
> > I believe that tracing the preempt_disable() in srcu_read_lock() and
> > srcu_read_unlock() is actually a good thing. Or am I missing your
> > point?
>
> Depends a bit on why we needed this change in the first place -- which,
> going by the other branch of this thread, seems lost. However,
> preempt_{dis,en}able_notrace() will not end up in any tracer/lockdep and
> generate the minimum code that preserves the required semantics.
True enough! But can all architectures locate the TIF in all contexts?
Thanx, Paul
next prev parent reply other threads:[~2015-10-06 21:03 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-06 16:13 [PATCH tip/core/rcu 0/13] Miscellaneous fixes for 4.4 Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 01/13] sched: Export sched_setscheduler_nocheck Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 02/13] rcu: Use rcu_callback_t in call_rcu*() and friends Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 03/13] rcu: Use call_rcu_func_t to replace explicit type equivalents Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 04/13] rcu: Don't disable preemption for Tiny and Tree RCU readers Paul E. McKenney
2015-10-06 16:20 ` [Kernel networking modules.] OSI levels 2 & 3, Assistance - If anyone knows anyone in the US. North West region John D Allen, Leveridge Systems INC
2015-10-06 16:44 ` [PATCH tip/core/rcu 04/13] rcu: Don't disable preemption for Tiny and Tree RCU readers Josh Triplett
2015-10-06 17:01 ` Paul E. McKenney
2015-10-06 17:16 ` Josh Triplett
2015-10-06 17:42 ` Paul E. McKenney
2015-10-06 17:46 ` Josh Triplett
2015-10-06 20:05 ` Peter Zijlstra
2015-10-06 20:18 ` Paul E. McKenney
2015-10-06 20:52 ` Peter Zijlstra
2015-10-06 21:05 ` Paul E. McKenney
2015-10-07 7:19 ` Peter Zijlstra
2015-10-06 16:13 ` [PATCH tip/core/rcu 05/13] rcu: Eliminate panic when silly boot-time fanout specified Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 06/13] rcu: Add online/offline info to stall warning message Paul E. McKenney
2015-10-06 17:15 ` Josh Triplett
2015-10-06 16:13 ` [PATCH tip/core/rcu 07/13] rcu: Move preemption disabling out of __srcu_read_lock() Paul E. McKenney
2015-10-06 17:18 ` Josh Triplett
2015-10-06 17:36 ` Paul E. McKenney
2015-10-06 17:43 ` Josh Triplett
2015-10-06 18:07 ` Paul E. McKenney
2015-10-06 20:07 ` Peter Zijlstra
2015-10-06 20:19 ` Paul E. McKenney
2015-10-06 20:32 ` Peter Zijlstra
2015-10-06 21:03 ` Paul E. McKenney [this message]
2015-10-07 7:20 ` Peter Zijlstra
2015-10-07 14:18 ` Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 08/13] rcu: Finish folding ->fqs_state into ->gp_state Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 09/13] rcu: Correct comment for values of ->gp_state field Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 10/13] rcu: Add rcu_pointer_handoff() Paul E. McKenney
2015-10-06 17:21 ` Josh Triplett
2015-10-06 17:31 ` Paul E. McKenney
2015-10-06 17:36 ` Josh Triplett
2015-10-06 20:27 ` Peter Zijlstra
2015-10-06 21:02 ` Paul E. McKenney
2015-10-07 7:22 ` Peter Zijlstra
2015-10-07 14:20 ` Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 11/13] rculist: Make list_entry_rcu() use lockless_dereference() Paul E. McKenney
2015-10-26 8:45 ` Ingo Molnar
2015-10-26 14:55 ` Paul E. McKenney
2015-10-26 18:02 ` Ingo Molnar
2015-10-27 3:37 ` Linus Torvalds
2015-10-27 5:19 ` Tejun Heo
2015-10-27 5:33 ` Paul E. McKenney
2015-10-28 8:33 ` Ingo Molnar
2015-10-28 20:35 ` Patrick Marlier
2015-10-29 0:00 ` Paul E. McKenney
2015-10-29 2:13 ` Tejun Heo
2015-10-28 20:58 ` [tip:core/rcu] fs/writeback, rcu: Don't use list_entry_rcu() for pointer offsetting in bdi_split_work_to_wbs() tip-bot for Tejun Heo
2015-10-27 5:32 ` [PATCH tip/core/rcu 11/13] rculist: Make list_entry_rcu() use lockless_dereference() Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 12/13] rcu: Remove deprecated rcu_lockdep_assert() Paul E. McKenney
2015-10-06 16:13 ` [PATCH tip/core/rcu 13/13] rculist: Use WRITE_ONCE() when deleting from reader-visible list Paul E. McKenney
2015-10-06 17:23 ` [PATCH tip/core/rcu 0/13] Miscellaneous fixes for 4.4 Josh Triplett
2015-10-06 17:38 ` Paul E. McKenney
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