[PATCH rcu 4/7] locktorture: Mark statistics data races

Paul E. McKenney
2021-07-21T21:04:51Z

The lock_stress_stats structure's ->n_lock_fail and ->n_lock_acquired
fields are incremented and sampled locklessly using plain C-language
statements, which KCSAN objects to. This commit therefore marks the
statistics gathering with data_race() to flag the intent. While in
the area, this commit also reduces the number of accesses to the
->n_lock_acquired field, thus eliminating some possible check/use
confusion.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/locking/locktorture.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index b3adb40549bf3..313d5e613fbe6 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -738,20 +738,22 @@ static int lock_torture_reader(void *arg)
static void __torture_print_stats(char *page,
struct lock_stress_stats *statp, bool write)
{
+ long cur;
bool fail = false;
int i, n_stress;
- long max = 0, min = statp ? statp[0].n_lock_acquired : 0;
+ long max = 0, min = statp ? data_race(statp[0].n_lock_acquired) : 0;
long long sum = 0;

n_stress = write ? cxt.nrealwriters_stress : cxt.nrealreaders_stress;
for (i = 0; i < n_stress; i++) {
- if (statp[i].n_lock_fail)
+ if (data_race(statp[i].n_lock_fail))
fail = true;
- sum += statp[i].n_lock_acquired;
- if (max < statp[i].n_lock_acquired)
- max = statp[i].n_lock_acquired;
- if (min > statp[i].n_lock_acquired)
- min = statp[i].n_lock_acquired;
+ cur = data_race(statp[i].n_lock_acquired);
+ sum += cur;
+ if (max < cur)
+ max = cur;
+ if (min > cur)
+ min = cur;
}
page += sprintf(page,
"%s: Total: %lld Max/Min: %ld/%ld %s Fail: %d %s\n",
--
2.31.1.189.g2e36527f23