From: Josh Triplett <josh@joshtriplett.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
tglx@linutronix.de, peterz@infradead.org, 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 10:18:39 -0700 [thread overview]
Message-ID: <20151006171839.GD9600@cloud> (raw)
In-Reply-To: <1444148028-11551-7-git-send-email-paulmck@linux.vnet.ibm.com>
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().
What restricted environments do you intend to invoke
__srcu_read_lock from?
This change seems fine, but I don't see any change in this patch series
that needs this, hence my curiosity.
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
> include/linux/srcu.h | 5 ++++-
> kernel/exit.c | 2 ++
> kernel/rcu/srcu.c | 2 --
> 3 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/srcu.h b/include/linux/srcu.h
> index bdeb4567b71e..f5f80c5643ac 100644
> --- a/include/linux/srcu.h
> +++ b/include/linux/srcu.h
> @@ -215,8 +215,11 @@ static inline int srcu_read_lock_held(struct srcu_struct *sp)
> */
> static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
> {
> - int retval = __srcu_read_lock(sp);
> + int retval;
>
> + preempt_disable();
> + retval = __srcu_read_lock(sp);
> + preempt_enable();
> rcu_lock_acquire(&(sp)->dep_map);
> return retval;
> }
> diff --git a/kernel/exit.c b/kernel/exit.c
> index ea95ee1b5ef7..0e93b63bbc59 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -761,7 +761,9 @@ void do_exit(long code)
> */
> flush_ptrace_hw_breakpoint(tsk);
>
> + TASKS_RCU(preempt_disable());
> TASKS_RCU(tasks_rcu_i = __srcu_read_lock(&tasks_rcu_exit_srcu));
> + TASKS_RCU(preempt_enable());
> exit_notify(tsk, group_dead);
> proc_exit_connector(tsk);
> #ifdef CONFIG_NUMA
> diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
> index 9e6122540d28..a63a1ea5a41b 100644
> --- a/kernel/rcu/srcu.c
> +++ b/kernel/rcu/srcu.c
> @@ -298,11 +298,9 @@ int __srcu_read_lock(struct srcu_struct *sp)
> int idx;
>
> idx = READ_ONCE(sp->completed) & 0x1;
> - preempt_disable();
> __this_cpu_inc(sp->per_cpu_ref->c[idx]);
> smp_mb(); /* B */ /* Avoid leaking the critical section. */
> __this_cpu_inc(sp->per_cpu_ref->seq[idx]);
> - preempt_enable();
> return idx;
> }
> EXPORT_SYMBOL_GPL(__srcu_read_lock);
> --
> 2.5.2
>
next prev parent reply other threads:[~2015-10-06 17:18 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 [this message]
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
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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