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authorPaul E. McKenney <paulmck@linux.ibm.com>2019-04-09 11:06:32 -0700
committerPaul E. McKenney <paulmck@linux.ibm.com>2019-05-28 09:06:09 -0700
commite8516c64fe97e27a28fd5bc65b616508ae0020cf (patch)
treea8735dcac32c1d817849495ab010617213de8657 /kernel
parent140e53f20b159722903f0c87358bcd809aa9767e (diff)
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rcutorture: Fix stutter_wait() return value and freelist checks
The stutter_wait() function is supposed to return true if it actually waits and false otherwise, but it instead unconditionally returns false. Which hides a bug in rcu_torture_writer() that fails to account for the fact that one of the rcu_tortures[] array elements will normally be referenced by rcu_torture_current, and thus not be on the freelist. This commit therefore corrects the stutter_wait() return value and adds a check for rcu_torture_current to rcu_torture_writer()'s check that things get freed after everything goes quiescent. In addition, this commit causes torture_stutter() to give a bit more than one second (instead of only one jiffy) warning of the end of the stutter interval. Finally, this commit disables long-delay readers and aggressive update-side forward-progress checks while forward-progress testing is in flight. Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/rcu/rcutorture.c16
-rw-r--r--kernel/torture.c17
2 files changed, 25 insertions, 8 deletions
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 7906ba2d9dad..954ac2b98619 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1010,10 +1010,13 @@ rcu_torture_writer(void *arg)
!rcu_gp_is_normal();
}
rcu_torture_writer_state = RTWS_STUTTER;
- if (stutter_wait("rcu_torture_writer"))
+ if (stutter_wait("rcu_torture_writer") &&
+ !READ_ONCE(rcu_fwd_cb_nodelay))
for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++)
- if (list_empty(&rcu_tortures[i].rtort_free))
- WARN_ON_ONCE(1);
+ if (list_empty(&rcu_tortures[i].rtort_free) &&
+ rcu_access_pointer(rcu_torture_current) !=
+ &rcu_tortures[i])
+ WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
} while (!torture_must_stop());
/* Reset expediting back to unexpedited. */
if (expediting > 0)
@@ -1709,6 +1712,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries)
}
/* Tight loop containing cond_resched(). */
+ WRITE_ONCE(rcu_fwd_cb_nodelay, true);
+ cur_ops->sync(); /* Later readers see above write. */
if (selfpropcb) {
WRITE_ONCE(fcs.stop, 0);
cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb);
@@ -1747,6 +1752,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries)
WARN_ON(READ_ONCE(fcs.stop) != 2);
destroy_rcu_head_on_stack(&fcs.rh);
}
+ schedule_timeout_uninterruptible(HZ / 10); /* Let kthreads recover. */
+ WRITE_ONCE(rcu_fwd_cb_nodelay, false);
}
/* Carry out call_rcu() forward-progress testing. */
@@ -1816,7 +1823,6 @@ static void rcu_torture_fwd_prog_cr(void)
cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */
(void)rcu_torture_fwd_prog_cbfree();
- WRITE_ONCE(rcu_fwd_cb_nodelay, false);
if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop)) {
WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED);
pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld\n",
@@ -1827,6 +1833,8 @@ static void rcu_torture_fwd_prog_cr(void)
n_max_gps, n_max_cbs, cver, gps);
rcu_torture_fwd_cb_hist();
}
+ schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */
+ WRITE_ONCE(rcu_fwd_cb_nodelay, false);
}
diff --git a/kernel/torture.c b/kernel/torture.c
index 17b2be9bde12..de0e0ecf88e1 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -578,10 +578,12 @@ static int stutter;
bool stutter_wait(const char *title)
{
int spt;
+ bool ret = false;
cond_resched_tasks_rcu_qs();
spt = READ_ONCE(stutter_pause_test);
for (; spt; spt = READ_ONCE(stutter_pause_test)) {
+ ret = true;
if (spt == 1) {
schedule_timeout_interruptible(1);
} else if (spt == 2) {
@@ -592,7 +594,7 @@ bool stutter_wait(const char *title)
}
torture_shutdown_absorb(title);
}
- return !!spt;
+ return ret;
}
EXPORT_SYMBOL_GPL(stutter_wait);
@@ -602,13 +604,20 @@ EXPORT_SYMBOL_GPL(stutter_wait);
*/
static int torture_stutter(void *arg)
{
+ int wtime;
+
VERBOSE_TOROUT_STRING("torture_stutter task started");
do {
if (!torture_must_stop() && stutter > 1) {
- WRITE_ONCE(stutter_pause_test, 1);
- schedule_timeout_interruptible(stutter - 1);
+ wtime = stutter;
+ if (stutter > HZ + 1) {
+ WRITE_ONCE(stutter_pause_test, 1);
+ wtime = stutter - HZ - 1;
+ schedule_timeout_interruptible(wtime);
+ wtime = HZ + 1;
+ }
WRITE_ONCE(stutter_pause_test, 2);
- schedule_timeout_interruptible(1);
+ schedule_timeout_interruptible(wtime);
}
WRITE_ONCE(stutter_pause_test, 0);
if (!torture_must_stop())