From 371f152c7ff76b99acbdf0decf5aa5ca1cc45bd6 Mon Sep 17 00:00:00 2001 From: Alex Richardson Date: Thu, 26 Nov 2020 13:31:57 +0000 Subject: Significantly speed up libthr/mutex_test and make more reliable Instead of using a simple global++ as the data race, with this change we perform the increment by loading the global, delaying for a bit and then storing back the incremented value. If I move the increment outside of the mutex protected range, I can now see the data race with only 100 iterations on amd64 in almost all cases. Before this change such a racy test almost always passed with < 100,000 iterations and only reliably failed with the current limit of 10 million. I noticed this poorly written test because the mutex:mutex{2,3} and timedmutex:mutex{2,3} tests were always timing out on our CheriBSD Jenkins. Writing good concurrency tests is hard so I won't attempt to do so, but this change should make the test more likely to fail if pthread_mutex_lock is not implemented correctly while also significantly reducing the time it takes to run these four tests. It will also reduce the time it takes for QEMU RISC-V testsuite runs by almost 40 minutes (out of currently 7 hours). Reviewed By: brooks, ngie Differential Revision: https://reviews.freebsd.org/D26473 --- contrib/netbsd-tests/lib/libpthread/t_mutex.c | 115 ++++++++++++++++++++++---- 1 file changed, 100 insertions(+), 15 deletions(-) (limited to 'contrib') diff --git a/contrib/netbsd-tests/lib/libpthread/t_mutex.c b/contrib/netbsd-tests/lib/libpthread/t_mutex.c index 3b8c8b72c727..ad841142f426 100644 --- a/contrib/netbsd-tests/lib/libpthread/t_mutex.c +++ b/contrib/netbsd-tests/lib/libpthread/t_mutex.c @@ -35,6 +35,9 @@ __RCSID("$NetBSD: t_mutex.c,v 1.15 2017/01/16 16:23:41 christos Exp $"); #include /* For UINT16_MAX */ #include #include +#ifdef __FreeBSD__ +#include +#endif #include #include #include @@ -128,16 +131,41 @@ ATF_TC_BODY(mutex1, tc) PTHREAD_REQUIRE(pthread_mutex_unlock(&mutex)); } +#ifdef __FreeBSD__ +/* + * Increment the value using a noinline function that includes a small delay + * to increase the window for the RMW data race. + */ +__noinline static int +increment(int value) +{ + for (volatile int i = 0; i < 100; i++) { + /* Small delay between read+write to increase chance of race */ + __compiler_membar(); + } + return value + 1; +} + +static volatile bool thread2_started = false; +#endif + static void * mutex2_threadfunc(void *arg) { long count = *(int *)arg; +#ifdef __FreeBSD__ + thread2_started = true; +#endif printf("2: Second thread (%p). Count is %ld\n", pthread_self(), count); while (count--) { PTHREAD_REQUIRE(mutex_lock(&mutex, &ts_lengthy)); +#ifdef __FreeBSD__ + global_x = increment(global_x); +#else global_x++; +#endif PTHREAD_REQUIRE(pthread_mutex_unlock(&mutex)); } @@ -153,16 +181,13 @@ ATF_TC_HEAD(mutex2, tc) atf_tc_set_md_var(tc, "timeout", "40"); #endif #endif - -#ifdef __FreeBSD__ -#if defined(__riscv) - atf_tc_set_md_var(tc, "timeout", "600"); -#endif -#endif } ATF_TC_BODY(mutex2, tc) { int count, count2; +#ifdef __FreeBSD__ + int num_increments; +#endif pthread_t new; void *joinval; @@ -177,18 +202,39 @@ ATF_TC_BODY(mutex2, tc) PTHREAD_REQUIRE(pthread_mutex_init(&mutex, NULL)); global_x = 0; +#ifdef __FreeBSD__ + num_increments = count = count2 = 1000; + if (getenv("NUM_ITERATIONS") != NULL) { + num_increments = count = count2 = + MIN(INT_MAX, strtoul(getenv("NUM_ITERATIONS"), NULL, 10)); + } + printf("Will use %d iterations\n", num_increments); +#else count = count2 = 10000000; +#endif PTHREAD_REQUIRE(mutex_lock(&mutex, &ts_lengthy)); +#ifdef __FreeBSD__ + thread2_started = false; +#endif PTHREAD_REQUIRE(pthread_create(&new, NULL, mutex2_threadfunc, &count2)); printf("1: Thread %p\n", pthread_self()); - +#ifdef __FreeBSD__ + while (!thread2_started) { + /* Wait for thread 2 to start to increase chance of race */ + } + printf("1: Unlocking to start increment loop %p\n", pthread_self()); +#endif PTHREAD_REQUIRE(pthread_mutex_unlock(&mutex)); while (count--) { PTHREAD_REQUIRE(mutex_lock(&mutex, &ts_lengthy)); +#ifdef __FreeBSD__ + global_x = increment(global_x); +#else global_x++; +#endif PTHREAD_REQUIRE(pthread_mutex_unlock(&mutex)); } @@ -197,7 +243,14 @@ ATF_TC_BODY(mutex2, tc) PTHREAD_REQUIRE(mutex_lock(&mutex, &ts_lengthy)); printf("1: Thread joined. X was %d. Return value (long) was %ld\n", global_x, (long)joinval); +#ifdef __FreeBSD__ + ATF_REQUIRE_EQ_MSG(count, -1, "%d", count); + ATF_REQUIRE_EQ_MSG((long)joinval, -1, "%ld", (long)joinval); + ATF_REQUIRE_EQ_MSG(global_x, num_increments * 2, "%d vs %d", global_x, + num_increments * 2); +#else ATF_REQUIRE_EQ(global_x, 20000000); +#endif #ifdef __NetBSD__ #if defined(__powerpc__) @@ -210,16 +263,27 @@ ATF_TC_BODY(mutex2, tc) #endif } +#ifdef __FreeBSD__ +static volatile bool thread3_started = false; +#endif + static void * mutex3_threadfunc(void *arg) { long count = *(int *)arg; +#ifdef __FreeBSD__ + thread3_started = true; +#endif printf("2: Second thread (%p). Count is %ld\n", pthread_self(), count); while (count--) { PTHREAD_REQUIRE(mutex_lock(&static_mutex, &ts_lengthy)); +#ifdef __FreeBSD__ + global_x = increment(global_x); +#else global_x++; +#endif PTHREAD_REQUIRE(pthread_mutex_unlock(&static_mutex)); } @@ -236,16 +300,13 @@ ATF_TC_HEAD(mutex3, tc) atf_tc_set_md_var(tc, "timeout", "40"); #endif #endif - -#ifdef __FreeBSD__ -#if defined(__riscv) - atf_tc_set_md_var(tc, "timeout", "600"); -#endif -#endif } ATF_TC_BODY(mutex3, tc) { int count, count2; +#ifdef __FreeBSD__ + int num_increments; +#endif pthread_t new; void *joinval; @@ -258,18 +319,36 @@ ATF_TC_BODY(mutex3, tc) #endif global_x = 0; +#ifdef __FreeBSD__ + num_increments = count = count2 = 1000; + if (getenv("NUM_ITERATIONS") != NULL) { + num_increments = count = count2 = + MIN(INT_MAX, strtoul(getenv("NUM_ITERATIONS"), NULL, 10)); + } + printf("Will use %d iterations\n", num_increments); +#else count = count2 = 10000000; +#endif PTHREAD_REQUIRE(mutex_lock(&static_mutex, &ts_lengthy)); PTHREAD_REQUIRE(pthread_create(&new, NULL, mutex3_threadfunc, &count2)); printf("1: Thread %p\n", pthread_self()); - +#ifdef __FreeBSD__ + while (!thread3_started) { + /* Wait for thread 3 to start to increase chance of race */ + } + printf("1: Unlocking to start increment loop %p\n", pthread_self()); +#endif PTHREAD_REQUIRE(pthread_mutex_unlock(&static_mutex)); while (count--) { PTHREAD_REQUIRE(mutex_lock(&static_mutex, &ts_lengthy)); +#ifdef __FreeBSD__ + global_x = increment(global_x); +#else global_x++; +#endif PTHREAD_REQUIRE(pthread_mutex_unlock(&static_mutex)); } @@ -278,8 +357,14 @@ ATF_TC_BODY(mutex3, tc) PTHREAD_REQUIRE(mutex_lock(&static_mutex, &ts_lengthy)); printf("1: Thread joined. X was %d. Return value (long) was %ld\n", global_x, (long)joinval); +#ifdef __FreeBSD__ + ATF_REQUIRE_EQ_MSG(count, -1, "%d", count); + ATF_REQUIRE_EQ_MSG((long)joinval, -1, "%ld", (long)joinval); + ATF_REQUIRE_EQ_MSG(global_x, num_increments * 2, "%d vs %d", global_x, + num_increments * 2); +#else ATF_REQUIRE_EQ(global_x, 20000000); - +#endif #ifdef __NetBSD__ #if defined(__powerpc__) /* XXX force a timeout in ppc case since an un-triggered race -- cgit v1.2.3