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Subject[PATCH v4 1/4] locktorture: Add nested_[un]lock() hooks and nlocks parameter
From
In order to extend locktorture to support lock nesting, add
nested_lock() and nested_unlock() hooks to the torture ops.

These take a 32bit lockset mask which is generated at random,
so some number of locks will be taken before the main lock is
taken and released afterwards.

Additionally, add nested_locks module parameter to allow
specifying the number of nested locks to be used.

This has been helpful to uncover issues in the proxy-exec
series development.

This was inspired by locktorture extensions originally implemented
by Connor O'Brien, for stress testing the proxy-execution series:
https://lore.kernel.org/lkml/20221003214501.2050087-12-connoro@google.com/

Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: kernel-team@android.com
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Co-developed-by: Connor O'Brien <connoro@google.com>
Signed-off-by: Connor O'Brien <connoro@google.com>
Signed-off-by: John Stultz <jstultz@google.com>
---
v3:
* Minor commit message tweaks and naming changes
suggested by Davidlohr Bueso
v4:
* Add co-developed tag
---
kernel/locking/locktorture.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 9c2fb613a55d..6fe046594868 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -48,6 +48,9 @@ torture_param(int, stat_interval, 60,
torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable");
torture_param(int, verbose, 1,
"Enable verbose debugging printk()s");
+torture_param(int, nested_locks, 0, "Number of nested locks (max = 8)");
+/* Going much higher trips "BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!" errors */
+#define MAX_NESTED_LOCKS 8

static char *torture_type = "spin_lock";
module_param(torture_type, charp, 0444);
@@ -76,10 +79,12 @@ static void lock_torture_cleanup(void);
struct lock_torture_ops {
void (*init)(void);
void (*exit)(void);
+ int (*nested_lock)(int tid, u32 lockset);
int (*writelock)(int tid);
void (*write_delay)(struct torture_random_state *trsp);
void (*task_boost)(struct torture_random_state *trsp);
void (*writeunlock)(int tid);
+ void (*nested_unlock)(int tid, u32 lockset);
int (*readlock)(int tid);
void (*read_delay)(struct torture_random_state *trsp);
void (*readunlock)(int tid);
@@ -669,6 +674,7 @@ static int lock_torture_writer(void *arg)
struct lock_stress_stats *lwsp = arg;
int tid = lwsp - cxt.lwsa;
DEFINE_TORTURE_RANDOM(rand);
+ u32 lockset_mask;

VERBOSE_TOROUT_STRING("lock_torture_writer task started");
set_user_nice(current, MAX_NICE);
@@ -677,7 +683,10 @@ static int lock_torture_writer(void *arg)
if ((torture_random(&rand) & 0xfffff) == 0)
schedule_timeout_uninterruptible(1);

+ lockset_mask = torture_random(&rand);
cxt.cur_ops->task_boost(&rand);
+ if (cxt.cur_ops->nested_lock)
+ cxt.cur_ops->nested_lock(tid, lockset_mask);
cxt.cur_ops->writelock(tid);
if (WARN_ON_ONCE(lock_is_write_held))
lwsp->n_lock_fail++;
@@ -690,6 +699,8 @@ static int lock_torture_writer(void *arg)
lock_is_write_held = false;
WRITE_ONCE(last_lock_release, jiffies);
cxt.cur_ops->writeunlock(tid);
+ if (cxt.cur_ops->nested_unlock)
+ cxt.cur_ops->nested_unlock(tid, lockset_mask);

stutter_wait("lock_torture_writer");
} while (!torture_must_stop());
@@ -830,11 +841,11 @@ lock_torture_print_module_parms(struct lock_torture_ops *cur_ops,
const char *tag)
{
pr_alert("%s" TORTURE_FLAG
- "--- %s%s: nwriters_stress=%d nreaders_stress=%d stat_interval=%d verbose=%d shuffle_interval=%d stutter=%d shutdown_secs=%d onoff_interval=%d onoff_holdoff=%d\n",
+ "--- %s%s: nwriters_stress=%d nreaders_stress=%d nested_locks=%d stat_interval=%d verbose=%d shuffle_interval=%d stutter=%d shutdown_secs=%d onoff_interval=%d onoff_holdoff=%d\n",
torture_type, tag, cxt.debug_lock ? " [debug]": "",
- cxt.nrealwriters_stress, cxt.nrealreaders_stress, stat_interval,
- verbose, shuffle_interval, stutter, shutdown_secs,
- onoff_interval, onoff_holdoff);
+ cxt.nrealwriters_stress, cxt.nrealreaders_stress,
+ nested_locks, stat_interval, verbose, shuffle_interval,
+ stutter, shutdown_secs, onoff_interval, onoff_holdoff);
}

static void lock_torture_cleanup(void)
@@ -1053,6 +1064,10 @@ static int __init lock_torture_init(void)
}
}

+ /* cap nested_locks to MAX_NESTED_LOCKS */
+ if (nested_locks > MAX_NESTED_LOCKS)
+ nested_locks = MAX_NESTED_LOCKS;
+
if (cxt.cur_ops->readlock) {
reader_tasks = kcalloc(cxt.nrealreaders_stress,
sizeof(reader_tasks[0]),
--
2.39.2.637.g21b0678d19-goog
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