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locktorture: Invoke percpu_free_rwsem() to do percpu-rwsem cleanup

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When executing the LOCK06 locktorture scenario featuring percpu-rwsem,
the RCU callback rcu_sync_func() may still be pending after locktorture
module is removed.  This can in turn 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

This commit avoids tis problem by adding an exit hook in lock_torture_ops
and using it to call percpu_free_rwsem() for percpu rwsem torture during
the module-cleanup function, thus ensuring that rcu_sync_func() completes
before module exits.

It is also necessary to call the exit hook if lock_torture_init()
fails half-way, so this commit also adds an ->init_called field in
lock_torture_cxt to indicate that exit hook, if present, must be called.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Hou Tao 2020-09-24 22:18:54 +08:00 committed by Paul E. McKenney
parent 85558182d5
commit 0d7202876b
1 changed files with 21 additions and 5 deletions
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26
kernel/locking/locktorture.c
View file

@ -76,6 +76,7 @@ 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);
@ -92,12 +93,13 @@ struct lock_torture_cxt {
int nrealwriters_stress;
int nrealreaders_stress;
bool debug_lock;
bool init_called;
atomic_t n_lock_torture_errors;
struct lock_torture_ops *cur_ops;
struct lock_stress_stats *lwsa; /* writer statistics */
struct lock_stress_stats *lrsa; /* reader statistics */
};
static struct lock_torture_cxt cxt = { 0, 0, false,
static struct lock_torture_cxt cxt = { 0, 0, false, false,
ATOMIC_INIT(0),
NULL, NULL};
/*
@ -573,6 +575,11 @@ static 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);
@ -597,6 +604,7 @@ 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,
@ -789,9 +797,10 @@ 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;
@ -831,6 +840,11 @@ static void lock_torture_cleanup(void)
cxt.lrsa = NULL;
end:
if (cxt.init_called) {
if (cxt.cur_ops->exit)
cxt.cur_ops->exit();
cxt.init_called = false;
}
torture_cleanup_end();
}
@ -878,8 +892,10 @@ static int __init lock_torture_init(void)
goto unwind;
}
if (cxt.cur_ops->init)
if (cxt.cur_ops->init) {
cxt.cur_ops->init();
cxt.init_called = true;
}
if (nwriters_stress >= 0)
cxt.nrealwriters_stress = nwriters_stress;