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Subject[PATCH 4.15 124/128] locking/locktorture: Fix num reader/writer corner cases
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Davidlohr Bueso <dave@stgolabs.net>


[ Upstream commit 2ce77d16db4240dd2e422fc0a5c26d3e2ec03446 ]

Things can explode for locktorture if the user does combinations
of nwriters_stress=0 nreaders_stress=0. Fix this by not assuming
we always want to torture writer threads.

Reported-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Jeremy Linton <jeremy.linton@arm.com>
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/locking/locktorture.c | 76 ++++++++++++++++++++++++-------------------
1 file changed, 44 insertions(+), 32 deletions(-)

--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -715,8 +715,7 @@ static void __torture_print_stats(char *
{
bool fail = 0;
int i, n_stress;
- long max = 0;
- long min = statp[0].n_lock_acquired;
+ long max = 0, min = statp ? statp[0].n_lock_acquired : 0;
long long sum = 0;

n_stress = write ? cxt.nrealwriters_stress : cxt.nrealreaders_stress;
@@ -823,7 +822,7 @@ static void lock_torture_cleanup(void)
* such, only perform the underlying torture-specific cleanups,
* and avoid anything related to locktorture.
*/
- if (!cxt.lwsa)
+ if (!cxt.lwsa && !cxt.lrsa)
goto end;

if (writer_tasks) {
@@ -898,6 +897,13 @@ static int __init lock_torture_init(void
firsterr = -EINVAL;
goto unwind;
}
+
+ if (nwriters_stress == 0 && nreaders_stress == 0) {
+ pr_alert("lock-torture: must run at least one locking thread\n");
+ firsterr = -EINVAL;
+ goto unwind;
+ }
+
if (cxt.cur_ops->init)
cxt.cur_ops->init();

@@ -921,17 +927,19 @@ static int __init lock_torture_init(void
#endif

/* Initialize the statistics so that each run gets its own numbers. */
+ if (nwriters_stress) {
+ lock_is_write_held = 0;
+ cxt.lwsa = kmalloc(sizeof(*cxt.lwsa) * cxt.nrealwriters_stress, GFP_KERNEL);
+ if (cxt.lwsa == NULL) {
+ VERBOSE_TOROUT_STRING("cxt.lwsa: Out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }

- lock_is_write_held = 0;
- cxt.lwsa = kmalloc(sizeof(*cxt.lwsa) * cxt.nrealwriters_stress, GFP_KERNEL);
- if (cxt.lwsa == NULL) {
- VERBOSE_TOROUT_STRING("cxt.lwsa: Out of memory");
- firsterr = -ENOMEM;
- goto unwind;
- }
- for (i = 0; i < cxt.nrealwriters_stress; i++) {
- cxt.lwsa[i].n_lock_fail = 0;
- cxt.lwsa[i].n_lock_acquired = 0;
+ for (i = 0; i < cxt.nrealwriters_stress; i++) {
+ cxt.lwsa[i].n_lock_fail = 0;
+ cxt.lwsa[i].n_lock_acquired = 0;
+ }
}

if (cxt.cur_ops->readlock) {
@@ -948,19 +956,21 @@ static int __init lock_torture_init(void
cxt.nrealreaders_stress = cxt.nrealwriters_stress;
}

- lock_is_read_held = 0;
- cxt.lrsa = kmalloc(sizeof(*cxt.lrsa) * cxt.nrealreaders_stress, GFP_KERNEL);
- if (cxt.lrsa == NULL) {
- VERBOSE_TOROUT_STRING("cxt.lrsa: Out of memory");
- firsterr = -ENOMEM;
- kfree(cxt.lwsa);
- cxt.lwsa = NULL;
- goto unwind;
- }
-
- for (i = 0; i < cxt.nrealreaders_stress; i++) {
- cxt.lrsa[i].n_lock_fail = 0;
- cxt.lrsa[i].n_lock_acquired = 0;
+ if (nreaders_stress) {
+ lock_is_read_held = 0;
+ cxt.lrsa = kmalloc(sizeof(*cxt.lrsa) * cxt.nrealreaders_stress, GFP_KERNEL);
+ if (cxt.lrsa == NULL) {
+ VERBOSE_TOROUT_STRING("cxt.lrsa: Out of memory");
+ firsterr = -ENOMEM;
+ kfree(cxt.lwsa);
+ cxt.lwsa = NULL;
+ goto unwind;
+ }
+
+ for (i = 0; i < cxt.nrealreaders_stress; i++) {
+ cxt.lrsa[i].n_lock_fail = 0;
+ cxt.lrsa[i].n_lock_acquired = 0;
+ }
}
}

@@ -990,12 +1000,14 @@ static int __init lock_torture_init(void
goto unwind;
}

- writer_tasks = kzalloc(cxt.nrealwriters_stress * sizeof(writer_tasks[0]),
- GFP_KERNEL);
- if (writer_tasks == NULL) {
- VERBOSE_TOROUT_ERRSTRING("writer_tasks: Out of memory");
- firsterr = -ENOMEM;
- goto unwind;
+ if (nwriters_stress) {
+ writer_tasks = kzalloc(cxt.nrealwriters_stress * sizeof(writer_tasks[0]),
+ GFP_KERNEL);
+ if (writer_tasks == NULL) {
+ VERBOSE_TOROUT_ERRSTRING("writer_tasks: Out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
}

if (cxt.cur_ops->readlock) {

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