From: Lai Jiangshan <laijs@cn.fujitsu.com>
To: paulmck@linux.vnet.ibm.com
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
linux-kernel@vger.kernel.org, mingo@elte.hu, dipankar@in.ibm.com,
akpm@linux-foundation.org, josh@joshtriplett.org,
dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de,
peterz@infradead.org, rostedt@goodmis.org,
Valdis.Kletnieks@vt.edu, dhowells@redhat.com,
eric.dumazet@gmail.com
Subject: Re: [PATCH tip/core/rcu 08/10] rcu: Add a TINY_PREEMPT_RCU
Date: Tue, 17 Aug 2010 17:36:13 +0800 [thread overview]
Message-ID: <4C6A580D.5010903@cn.fujitsu.com> (raw)
In-Reply-To: <20100816222402.GM2388@linux.vnet.ibm.com>
On 08/17/2010 06:24 AM, Paul E. McKenney wrote:
>> --(t->rcu_read_lock_nesting)
>>
>> could be split in two distinct operations:
>>
>> read t->rcu_read_lock_nesting
>> decrement t->rcu_read_lock_nesting
>>
>> Note that in order to know the result required to pass the sequence
>> point "&&" (the test), we only need to perform the read, not the
>> decrement. AFAIU, gcc would be in its rights to move the
>> t->rcu_read_lock_nesting update after the volatile access.
>
> I will run this by some compiler experts.
>
We can just use "read and decrement statements" instead of "--" to
avoid dependency from compilers.
next prev parent reply other threads:[~2010-08-17 9:32 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-09 22:14 [PATCH tip/core/rcu 0/N] Additional RCU commits queued for 2.6.37 Paul E. McKenney
2010-08-09 22:15 ` [PATCH tip/core/rcu 01/10] rcu head remove init Paul E. McKenney
2010-08-09 22:15 ` [PATCH tip/core/rcu 02/10] Update documentation to note the passage of INIT_RCU_HEAD() Paul E. McKenney
2010-08-09 22:15 ` [PATCH tip/core/rcu 03/10] Update call_rcu() usage, add synchronize_rcu() Paul E. McKenney
2010-08-09 22:15 ` [PATCH tip/core/rcu 04/10] rcu: allow RCU CPU stall warning messages to be controlled in /sys Paul E. McKenney
2010-08-09 22:15 ` [PATCH tip/core/rcu 05/10] rcu: restrict TREE_RCU to SMP builds with !PREEMPT Paul E. McKenney
2010-08-09 22:15 ` [PATCH tip/core/rcu 06/10] rcu: Allow RCU CPU stall warnings to be off at boot, but manually enablable Paul E. McKenney
2010-08-09 22:15 ` [PATCH tip/core/rcu 07/10] rcu: Fix RCU_FANOUT help message Paul E. McKenney
2010-08-09 22:15 ` [PATCH tip/core/rcu 08/10] rcu: Add a TINY_PREEMPT_RCU Paul E. McKenney
2010-08-16 15:07 ` Mathieu Desnoyers
2010-08-16 18:33 ` Paul E. McKenney
2010-08-16 19:19 ` Mathieu Desnoyers
2010-08-16 21:32 ` Paul E. McKenney
2010-08-16 21:41 ` Mathieu Desnoyers
2010-08-16 21:55 ` Paul E. McKenney
2010-08-16 22:07 ` Mathieu Desnoyers
2010-08-16 22:24 ` Paul E. McKenney
2010-08-17 9:36 ` Lai Jiangshan [this message]
2010-08-17 14:35 ` Paul E. McKenney
2010-08-17 13:27 ` Steven Rostedt
2010-08-17 14:16 ` Mathieu Desnoyers
2010-08-17 14:54 ` Steven Rostedt
2010-08-17 15:55 ` Mathieu Desnoyers
2010-08-17 16:04 ` Steven Rostedt
2010-08-17 16:06 ` Steven Rostedt
2010-08-17 16:25 ` Mathieu Desnoyers
2010-08-17 19:33 ` Paul E. McKenney
2010-08-17 20:00 ` Paul E. McKenney
2010-08-09 22:15 ` [PATCH tip/core/rcu 09/10] rcu: update obsolete rcu_read_lock() comment Paul E. McKenney
2010-08-16 14:45 ` Mathieu Desnoyers
2010-08-16 17:55 ` Paul E. McKenney
2010-08-16 18:24 ` Mathieu Desnoyers
2010-08-09 22:15 ` [PATCH tip/core/rcu 10/10] rcu: refer RCU CPU stall-warning victims to stallwarn.txt Paul E. McKenney
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