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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2009-09-13 09:15:10 -0700 |
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committer | Ingo Molnar <mingo@elte.hu> | 2009-09-18 00:06:33 +0200 |
commit | c3422bea5f09b0e85704f51f2b01271630b8940b (patch) | |
tree | fc4a18241b0f7f5d71211f6787428197769cb9f5 /kernel/rcutree.c | |
parent | b0e165c035b13e1074fa0b555318bd9cb7102558 (diff) | |
download | linux-stable-c3422bea5f09b0e85704f51f2b01271630b8940b.tar.gz linux-stable-c3422bea5f09b0e85704f51f2b01271630b8940b.tar.bz2 linux-stable-c3422bea5f09b0e85704f51f2b01271630b8940b.zip |
rcu: Simplify rcu_read_unlock_special() quiescent-state accounting
The earlier approach required two scheduling-clock ticks to note an
preemptable-RCU quiescent state in the situation in which the
scheduling-clock interrupt is unlucky enough to always interrupt an
RCU read-side critical section.
With this change, the quiescent state is instead noted by the
outermost rcu_read_unlock() immediately following the first
scheduling-clock tick, or, alternatively, by the first subsequent
context switch. Therefore, this change also speeds up grace
periods.
Suggested-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
LKML-Reference: <12528585111945-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcutree.c')
-rw-r--r-- | kernel/rcutree.c | 15 |
1 files changed, 6 insertions, 9 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index e9a4ae94647f..6c99553e9f15 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -107,27 +107,23 @@ static void __cpuinit rcu_init_percpu_data(int cpu, struct rcu_state *rsp, */ void rcu_sched_qs(int cpu) { - unsigned long flags; struct rcu_data *rdp; - local_irq_save(flags); rdp = &per_cpu(rcu_sched_data, cpu); - rdp->passed_quiesc = 1; rdp->passed_quiesc_completed = rdp->completed; - rcu_preempt_qs(cpu); - local_irq_restore(flags); + barrier(); + rdp->passed_quiesc = 1; + rcu_preempt_note_context_switch(cpu); } void rcu_bh_qs(int cpu) { - unsigned long flags; struct rcu_data *rdp; - local_irq_save(flags); rdp = &per_cpu(rcu_bh_data, cpu); - rdp->passed_quiesc = 1; rdp->passed_quiesc_completed = rdp->completed; - local_irq_restore(flags); + barrier(); + rdp->passed_quiesc = 1; } #ifdef CONFIG_NO_HZ @@ -615,6 +611,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags) /* Advance to a new grace period and initialize state. */ rsp->gpnum++; + WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT); rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; record_gp_stall_check_time(rsp); |