Commit-ID: 4ced3314fd3a73dabac4e8a41747883eff36c3e8
Gitweb: https://git.kernel.org/tip/4ced3314fd3a73dabac4e8a41747883eff36c3e8
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Tue, 21 Nov 2017 15:01:02 -0800
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon, 11 Dec 2017 09:18:29 -0800
torture: Make stutter less vulnerable to compilers and races
The stutter_wait() function repeatedly fetched stutter_pause_test, and
should really just fetch it once on each pass. The races should be
harmless, but why have the races? Also, the whole point of the value
"2" for stutter_pause_test is to get everyone to start at very nearly
the same time, but the value "2" was the first jiffy of the stutter
rather than the last jiffy of the stutter.
This commit rearranges the code to be more sensible.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/torture.c | 33 +++++++++++++++++----------------
1 file changed, 17 insertions(+), 16 deletions(-)
diff --git a/kernel/torture.c b/kernel/torture.c
index 52781e8..3bcbd4f 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -573,18 +573,21 @@ static int stutter;
*/
void stutter_wait(const char *title)
{
+ int spt;
+
cond_resched_rcu_qs();
- while (READ_ONCE(stutter_pause_test) ||
- (torture_runnable && !READ_ONCE(*torture_runnable))) {
- if (stutter_pause_test)
- if (READ_ONCE(stutter_pause_test) == 1)
- schedule_timeout_interruptible(1);
- else
- while (READ_ONCE(stutter_pause_test))
- cond_resched();
- else
+ spt = READ_ONCE(stutter_pause_test);
+ while (spt || (torture_runnable && !READ_ONCE(*torture_runnable))) {
+ if (spt == 1) {
+ schedule_timeout_interruptible(1);
+ } else if (spt == 2) {
+ while (READ_ONCE(stutter_pause_test))
+ cond_resched();
+ } else {
schedule_timeout_interruptible(round_jiffies_relative(HZ));
+ }
torture_shutdown_absorb(title);
+ spt = READ_ONCE(stutter_pause_test);
}
}
EXPORT_SYMBOL_GPL(stutter_wait);
@@ -597,17 +600,15 @@ static int torture_stutter(void *arg)
{
VERBOSE_TOROUT_STRING("torture_stutter task started");
do {
- if (!torture_must_stop()) {
- if (stutter > 1) {
- schedule_timeout_interruptible(stutter - 1);
- WRITE_ONCE(stutter_pause_test, 2);
- }
- schedule_timeout_interruptible(1);
+ if (!torture_must_stop() && stutter > 1) {
WRITE_ONCE(stutter_pause_test, 1);
+ schedule_timeout_interruptible(stutter - 1);
+ WRITE_ONCE(stutter_pause_test, 2);
+ schedule_timeout_interruptible(1);
}
+ WRITE_ONCE(stutter_pause_test, 0);
if (!torture_must_stop())
schedule_timeout_interruptible(stutter);
- WRITE_ONCE(stutter_pause_test, 0);
torture_shutdown_absorb("torture_stutter");
} while (!torture_must_stop());
torture_kthread_stopping("torture_stutter");
--
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