rcutorture: Fix rcutorture shutdown races
Not all of the rcutorture kthreads waited for kthread_should_stop()
before returning from their top-level functions, and none of them
used torture_shutdown_absorb() properly. These problems can result in
segfaults and hangs at shutdown time, and some recent changes perturbed
timing sufficiently to make them much more probable. This commit
therefore creates a torture_kthread_stopping() function that does the
proper kthread shutdown dance in one centralized location.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/include/linux/torture.h b/include/linux/torture.h
index 513b85f..db9bc77 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -45,7 +45,7 @@
#define TOROUT_STRING(s) \
pr_alert("%s" TORTURE_FLAG s "\n", torture_type)
#define VERBOSE_TOROUT_STRING(s) \
- do { if (verbose) pr_alert("%s" TORTURE_FLAG s "\n", torture_type); } while (0)
+ do { if (verbose) pr_alert("%s" TORTURE_FLAG " %s\n", torture_type, s); } while (0)
#define VERBOSE_TOROUT_ERRSTRING(s) \
do { if (verbose) pr_alert("%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
@@ -88,5 +88,6 @@
bool torture_cleanup(void);
bool torture_must_stop(void);
bool torture_must_stop_irq(void);
+void torture_kthread_stopping(char *title);
#endif /* __LINUX_TORTURE_H */
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index dbb4437..2680dbd 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -601,12 +601,13 @@
} while (!torture_must_stop());
/* Clean up and exit. */
- VERBOSE_TOROUT_STRING("rcu_torture_boost task stopping");
- torture_shutdown_absorb("rcu_torture_boost");
- while (!kthread_should_stop() || rbi.inflight)
+ while (!kthread_should_stop() || rbi.inflight) {
+ torture_shutdown_absorb("rcu_torture_boost");
schedule_timeout_uninterruptible(1);
+ }
smp_mb(); /* order accesses to ->inflight before stack-frame death. */
destroy_rcu_head_on_stack(&rbi.rcu);
+ torture_kthread_stopping("rcu_torture_boost");
return 0;
}
@@ -637,10 +638,7 @@
}
stutter_wait("rcu_torture_fqs");
} while (!torture_must_stop());
- VERBOSE_TOROUT_STRING("rcu_torture_fqs task stopping");
- torture_shutdown_absorb("rcu_torture_fqs");
- while (!kthread_should_stop())
- schedule_timeout_uninterruptible(1);
+ torture_kthread_stopping("rcu_torture_fqs");
return 0;
}
@@ -709,10 +707,7 @@
rcutorture_record_progress(++rcu_torture_current_version);
stutter_wait("rcu_torture_writer");
} while (!torture_must_stop());
- VERBOSE_TOROUT_STRING("rcu_torture_writer task stopping");
- torture_shutdown_absorb("rcu_torture_writer");
- while (!kthread_should_stop())
- schedule_timeout_uninterruptible(1);
+ torture_kthread_stopping("rcu_torture_writer");
return 0;
}
@@ -747,10 +742,7 @@
stutter_wait("rcu_torture_fakewriter");
} while (!torture_must_stop());
- VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task stopping");
- torture_shutdown_absorb("rcu_torture_fakewriter");
- while (!kthread_should_stop())
- schedule_timeout_uninterruptible(1);
+ torture_kthread_stopping("rcu_torture_fakewriter");
return 0;
}
@@ -891,12 +883,9 @@
schedule();
stutter_wait("rcu_torture_reader");
} while (!torture_must_stop());
- VERBOSE_TOROUT_STRING("rcu_torture_reader task stopping");
- torture_shutdown_absorb("rcu_torture_reader");
if (irqreader && cur_ops->irq_capable)
del_timer_sync(&t);
- while (!kthread_should_stop())
- schedule_timeout_uninterruptible(1);
+ torture_kthread_stopping("rcu_torture_reader");
return 0;
}
@@ -1009,7 +998,7 @@
rcu_torture_stats_print();
torture_shutdown_absorb("rcu_torture_stats");
} while (!torture_must_stop());
- VERBOSE_TOROUT_STRING("rcu_torture_stats task stopping");
+ torture_kthread_stopping("rcu_torture_stats");
return 0;
}
@@ -1170,12 +1159,9 @@
if (atomic_dec_and_test(&barrier_cbs_count))
wake_up(&barrier_wq);
} while (!torture_must_stop());
- VERBOSE_TOROUT_STRING("rcu_torture_barrier_cbs task stopping");
- torture_shutdown_absorb("rcu_torture_barrier_cbs");
- while (!kthread_should_stop())
- schedule_timeout_interruptible(1);
cur_ops->cb_barrier();
destroy_rcu_head_on_stack(&rcu);
+ torture_kthread_stopping("rcu_torture_barrier_cbs");
return 0;
}
@@ -1206,10 +1192,7 @@
n_barrier_successes++;
schedule_timeout_interruptible(HZ / 10);
} while (!torture_must_stop());
- VERBOSE_TOROUT_STRING("rcu_torture_barrier task stopping");
- torture_shutdown_absorb("rcu_torture_barrier");
- while (!kthread_should_stop())
- schedule_timeout_interruptible(1);
+ torture_kthread_stopping("rcu_torture_barrier");
return 0;
}
diff --git a/kernel/torture.c b/kernel/torture.c
index 12a5807..6f1c660 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -169,7 +169,7 @@
}
schedule_timeout_interruptible(onoff_interval);
}
- VERBOSE_TOROUT_STRING("torture_onoff task stopping");
+ torture_kthread_stopping("torture_onoff");
return 0;
}
@@ -370,7 +370,7 @@
torture_shuffle_tasks();
torture_shutdown_absorb("torture_shuffle");
} while (!torture_must_stop());
- VERBOSE_TOROUT_STRING("torture_shuffle task stopping");
+ torture_kthread_stopping("torture_shuffle");
return 0;
}
@@ -465,7 +465,7 @@
jiffies_snap = jiffies;
}
if (torture_must_stop()) {
- VERBOSE_TOROUT_STRING("torture_shutdown task stopping");
+ torture_kthread_stopping("torture_shutdown");
return 0;
}
@@ -583,7 +583,7 @@
ACCESS_ONCE(stutter_pause_test) = 0;
torture_shutdown_absorb("torture_stutter");
} while (!torture_must_stop());
- VERBOSE_TOROUT_STRING("torture_stutter task stopping");
+ torture_kthread_stopping("torture_stutter");
return 0;
}
@@ -696,3 +696,21 @@
return ACCESS_ONCE(fullstop) != FULLSTOP_DONTSTOP;
}
EXPORT_SYMBOL_GPL(torture_must_stop_irq);
+
+/*
+ * Each kthread must wait for kthread_should_stop() before returning from
+ * its top-level function, otherwise segfaults ensue. This function
+ * prints a "stopping" message and waits for kthread_should_stop(), and
+ * should be called from all torture kthreads immediately prior to
+ * returning.
+ */
+void torture_kthread_stopping(char *title)
+{
+ if (verbose)
+ pr_alert("%s" TORTURE_FLAG " %s\n", torture_type, title);
+ while (!kthread_should_stop()) {
+ torture_shutdown_absorb(title);
+ schedule_timeout_uninterruptible(1);
+ }
+}
+EXPORT_SYMBOL_GPL(torture_kthread_stopping);
