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Subject[tip:core/urgent] rcutorture: Occasionally delay readers enough to make RCU force_quiescent_state
Commit-ID:  f4a82a059aea43947d4f37dba9da1782d11caece
Gitweb: http://git.kernel.org/tip/f4a82a059aea43947d4f37dba9da1782d11caece
Author: Josh Triplett <josh@joshtriplett.org>
AuthorDate: Tue, 8 Sep 2009 15:54:35 -0700
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Sat, 12 Sep 2009 09:47:07 +0200

rcutorture: Occasionally delay readers enough to make RCU force_quiescent_state

rcutorture already delays readers, but never for long enough to
make RCU force a quiescent state. Add an occasional delay of
50ms.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: josht@linux.vnet.ibm.com
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
LKML-Reference: <12524504772607-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
kernel/rcutorture.c | 15 +++++++++------
1 files changed, 9 insertions(+), 6 deletions(-)
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index b33db53..328a825 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -281,14 +281,17 @@ static int rcu_torture_read_lock(void) __acquires(RCU)

static void rcu_read_delay(struct rcu_random_state *rrsp)
{
- long delay;
- const long longdelay = 200;
+ const unsigned long shortdelay_us = 200;
+ const unsigned long longdelay_ms = 50;

- /* We want there to be long-running readers, but not all the time. */
+ /* We want a short delay sometimes to make a reader delay the grace
+ * period, and we want a long delay occasionally to trigger
+ * force_quiescent_state. */

- delay = rcu_random(rrsp) % (nrealreaders * 2 * longdelay);
- if (!delay)
- udelay(longdelay);
+ if (!(rcu_random(rrsp) % (nrealreaders * 2000 * longdelay_ms)))
+ mdelay(longdelay_ms);
+ if (!(rcu_random(rrsp) % (nrealreaders * 2 * shortdelay_us)))
+ udelay(shortdelay_us);
}

static void rcu_torture_read_unlock(int idx) __releases(RCU)

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