When do percpu-rwsem writer lock torture, the RCU callback
rcu_sync_func() may still be pending after locktorture module
is removed, and it will lead to the following Oops:
BUG: unable to handle page fault for address: ffffffffc00eb920
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 6500a067 P4D 6500a067 PUD 6500c067 PMD 13a36c067 PTE 800000013691c163
Oops: 0000 [#1] PREEMPT SMP
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.9.0-rc5+ #4
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
RIP: 0010:rcu_cblist_dequeue+0x12/0x30
Call Trace:
<IRQ>
rcu_core+0x1b1/0x860
__do_softirq+0xfe/0x326
asm_call_on_stack+0x12/0x20
</IRQ>
do_softirq_own_stack+0x5f/0x80
irq_exit_rcu+0xaf/0xc0
sysvec_apic_timer_interrupt+0x2e/0xb0
asm_sysvec_apic_timer_interrupt+0x12/0x20
Fix it by adding an exit hook in lock_torture_ops and
use it to call percpu_free_rwsem() for percpu rwsem torture
before the module is removed, so we can ensure rcu_sync_func()
completes before module exits.
Also needs to call exit hook if lock_torture_init() fails half-way,
so use ctx->cur_ops != NULL to signal that init hook has been called.
Signed-off-by: Hou Tao <hout...@huawei.com>
---
kernel/locking/locktorture.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)
diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index bebdf98e6cd78..e91033e9b6f95 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -74,6 +74,7 @@ static void lock_torture_cleanup(void);
*/
struct lock_torture_ops {
void (*init)(void);
+ void (*exit)(void);
int (*writelock)(void);
void (*write_delay)(struct torture_random_state *trsp);
void (*task_boost)(struct torture_random_state *trsp);
@@ -571,6 +572,11 @@ void torture_percpu_rwsem_init(void)
BUG_ON(percpu_init_rwsem(&pcpu_rwsem));
}
+static void torture_percpu_rwsem_exit(void)
+{
+ percpu_free_rwsem(&pcpu_rwsem);
+}
+
static int torture_percpu_rwsem_down_write(void) __acquires(pcpu_rwsem)
{
percpu_down_write(&pcpu_rwsem);
@@ -595,6 +601,7 @@ static void torture_percpu_rwsem_up_read(void)
__releases(pcpu_rwsem)
static struct lock_torture_ops percpu_rwsem_lock_ops = {
.init = torture_percpu_rwsem_init,
+ .exit = torture_percpu_rwsem_exit,
.writelock = torture_percpu_rwsem_down_write,
.write_delay = torture_rwsem_write_delay,
.task_boost = torture_boost_dummy,
@@ -786,9 +793,10 @@ static void lock_torture_cleanup(void)
/*
* Indicates early cleanup, meaning that the test has not run,
- * such as when passing bogus args when loading the module. As
- * such, only perform the underlying torture-specific cleanups,
- * and avoid anything related to locktorture.
+ * such as when passing bogus args when loading the module.
+ * However cxt->cur_ops.init() may have been invoked, so beside
+ * perform the underlying torture-specific cleanups, cur_ops.exit()
+ * will be invoked if needed.
*/
if (!cxt.lwsa && !cxt.lrsa)
goto end;
@@ -828,6 +836,12 @@ static void lock_torture_cleanup(void)
cxt.lrsa = NULL;
end:
+ /* If init() has been called, then do exit() accordingly */
+ if (cxt.cur_ops) {
+ if (cxt.cur_ops->exit)
+ cxt.cur_ops->exit();
+ cxt.cur_ops = NULL;
+ }
torture_cleanup_end();
}
@@ -835,6 +849,7 @@ static int __init lock_torture_init(void)
{
int i, j;
int firsterr = 0;
+ struct lock_torture_ops *cur_ops;
static struct lock_torture_ops *torture_ops[] = {
&lock_busted_ops,
&spin_lock_ops, &spin_lock_irq_ops,
@@ -853,8 +868,8 @@ static int __init lock_torture_init(void)
/* Process args and tell the world that the torturer is on the job. */
for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
- cxt.cur_ops = torture_ops[i];
- if (strcmp(torture_type, cxt.cur_ops->name) == 0)
+ cur_ops = torture_ops[i];
+ if (strcmp(torture_type, cur_ops->name) == 0)
break;
}
if (i == ARRAY_SIZE(torture_ops)) {
@@ -869,12 +884,13 @@ static int __init lock_torture_init(void)
}
if (nwriters_stress == 0 &&
- (!cxt.cur_ops->readlock || nreaders_stress == 0)) {
+ (!cur_ops->readlock || nreaders_stress == 0)) {
pr_alert("lock-torture: must run at least one locking
thread\n");
firsterr = -EINVAL;
goto unwind;
}
+ cxt.cur_ops = cur_ops;
if (cxt.cur_ops->init)
cxt.cur_ops->init();
--
2.25.0.4.g0ad7144999
