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Commit 7fafaac5 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

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.

Accommodate this grouping by making VERBOSE_TOROUT_STRING() capable of
taking a non-const string as its argument, which allows the new
torture_kthread_stopping() to pass its "title" argument directly to
the updated version of VERBOSE_TOROUT_STRING().

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 14562d1c

include/linux/torture.h

+2 −1
Original line number Diff line number Diff line
@@ -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 @@ void torture_init_end(void); 
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 */

kernel/rcu/rcutorture.c

+11 −28
Original line number Diff line number Diff line
@@ -602,12 +602,13 @@ checkwait: stutter_wait("rcu_torture_boost"); 
	} while (!torture_must_stop());



	/* Clean up and exit. */

	VERBOSE_TOROUT_STRING("rcu_torture_boost task stopping");

	while (!kthread_should_stop() || rbi.inflight) {

		torture_shutdown_absorb("rcu_torture_boost");

	while (!kthread_should_stop() || rbi.inflight)

		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;

}
@@ -638,10 +639,7 @@ rcu_torture_fqs(void *arg) 
		}

		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;

}
@@ -710,10 +708,7 @@ rcu_torture_writer(void *arg) 
		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;

}
@@ -748,10 +743,7 @@ rcu_torture_fakewriter(void *arg) 
		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;

}
@@ -892,12 +884,9 @@ rcu_torture_reader(void *arg) 
		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;

}
@@ -1010,7 +999,7 @@ rcu_torture_stats(void *arg) 
		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;

}
@@ -1171,12 +1160,9 @@ static int rcu_torture_barrier_cbs(void *arg) 
		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;

}
@@ -1207,10 +1193,7 @@ static int rcu_torture_barrier(void *arg) 
		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;

}

kernel/torture.c

+22 −4
Original line number Diff line number Diff line
@@ -169,7 +169,7 @@ torture_onoff(void *arg) 
		}

		schedule_timeout_interruptible(onoff_interval);

	}

	VERBOSE_TOROUT_STRING("torture_onoff task stopping");

	torture_kthread_stopping("torture_onoff");

	return 0;

}
@@ -370,7 +370,7 @@ static int torture_shuffle(void *arg) 
		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 @@ static int torture_shutdown(void *arg) 
		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 @@ static int torture_stutter(void *arg) 
		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 @@ bool torture_must_stop_irq(void) 
	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)

		VERBOSE_TOROUT_STRING(title);

	while (!kthread_should_stop()) {

		torture_shutdown_absorb(title);

		schedule_timeout_uninterruptible(1);

	}

}

EXPORT_SYMBOL_GPL(torture_kthread_stopping);