From: Jan S. <jst...@re...> - 2013-10-03 11:32:19
|
Remove all gotos and if there's error in any of pthread functions exit immediately. Signed-off-by: Jan Stancek <jst...@re...> --- .../interfaces/pthread_attr_setschedpolicy/2-1.c | 105 +++++++------------- 1 files changed, 34 insertions(+), 71 deletions(-) diff --git a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c index 6088466..6c471d6 100644 --- a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c +++ b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c @@ -24,6 +24,7 @@ #include <string.h> #include <pthread.h> #include <unistd.h> +#include <stdlib.h> #include <errno.h> #include <posixtest.h> @@ -40,8 +41,10 @@ static pthread_cond_t cond = PTHREAD_COND_INITIALIZER; static int thread_started; -#define ERR_MSG(f, rc) printf("Failed: function: %s status: %s(%u)\n", \ - f, strerror(rc), rc) +#define FAIL_AND_EXIT(f, rc) { \ + printf("Failed: function: %s status: %s(%u)\n", f, strerror(rc), rc); \ + exit(PTS_UNRESOLVED); \ +} static void *thread_func(void *data) { @@ -50,23 +53,17 @@ static void *thread_func(void *data) int rc; rc = pthread_getschedparam(pthread_self(), &policy, &sp); - if (rc) { - ERR_MSG("pthread_getschedparam()", rc); - goto done; - } + if (rc) + FAIL_AND_EXIT("pthread_getschedparam()", rc); thread_started = 1; rc = pthread_cond_signal(&cond); - if (rc) { - ERR_MSG("pthread_cond_signal()", rc); - goto done; - } + if (rc) + FAIL_AND_EXIT("pthread_cond_signal()", rc); rc = pthread_mutex_lock(&mutex); - if (rc) { - ERR_MSG("pthread_mutex_lock()", rc); - goto done; - } + if (rc) + FAIL_AND_EXIT("pthread_mutex_lock()", rc); /* Stuff the priority in execution order */ if (!priorities[0]) @@ -77,79 +74,58 @@ static void *thread_func(void *data) priorities[2] = sp.sched_priority; rc = pthread_mutex_unlock(&mutex); - if (rc) { - ERR_MSG("pthread_mutex_unlock()", rc); - goto done; - } + if (rc) + FAIL_AND_EXIT("pthread_mutex_unlock()", rc); -done: return (void *)(long)rc; } static int create_thread(int prio, pthread_t * tid) { int rc; - char *func; struct sched_param sp; pthread_attr_t attr; - func = "pthread_attr_init()"; rc = pthread_attr_init(&attr); if (rc != 0) - goto done; + FAIL_AND_EXIT("pthread_attr_init()", rc); - func = "pthread_attr_setschedpolicy()"; rc = pthread_attr_setschedpolicy(&attr, SCHED_FIFO); if (rc != 0) - goto error; + FAIL_AND_EXIT("pthread_attr_setschedpolicy()", rc); - func = "pthread_attr_setinheritsched()"; rc = pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED); if (rc != 0) - goto error; + FAIL_AND_EXIT("pthread_attr_setinheritsched()", rc); - func = "pthread_attr_setschedparam()"; sp.sched_priority = prio; rc = pthread_attr_setschedparam(&attr, &sp); if (rc != 0) - goto error; + FAIL_AND_EXIT("pthread_attr_setschedparam()", rc); thread_started = 0; rc = pthread_create(tid, &attr, thread_func, NULL); - if (rc) { - ERR_MSG("pthread_create()", rc); - goto error; - } + if (rc) + FAIL_AND_EXIT("pthread_create()", rc); while (!thread_started) { - func = "pthread_mutex_lock()"; rc = pthread_mutex_lock(&c_mutex); if (rc) - goto error; + FAIL_AND_EXIT("pthread_mutex_lock()", rc); - func = "pthread_cond_wait()"; rc = pthread_cond_wait(&cond, &c_mutex); if (rc) - goto unlock; + FAIL_AND_EXIT("pthread_cond_wait()", rc); - func = "pthread_mutex_unlock()"; rc = pthread_mutex_unlock(&c_mutex); if (rc) - goto error; + FAIL_AND_EXIT("pthread_mutex_unlock()", rc); } pthread_attr_destroy(&attr); return 0; - -unlock: - (void)pthread_mutex_unlock(&c_mutex); -error: - pthread_attr_destroy(&attr); -done: - ERR_MSG(func, rc); - return -1; } int main(void) @@ -166,48 +142,36 @@ int main(void) status = PTS_UNRESOLVED; rc = pthread_mutex_lock(&mutex); - if (rc) { - ERR_MSG("pthread_mutex_lock()", rc); - goto done; - } + if (rc) + FAIL_AND_EXIT("pthread_mutex_lock()", rc); rc = create_thread(PRIO_LOW, &t3); if (rc) - goto done; + FAIL_AND_EXIT("create_thread LOW", rc); rc = create_thread(PRIO_MED, &t2); if (rc) - goto done; + FAIL_AND_EXIT("create_thread MED", rc); rc = create_thread(PRIO_HIGH, &t1); if (rc) - goto done; + FAIL_AND_EXIT("create_thread HIGH", rc); rc = pthread_mutex_unlock(&mutex); if (rc) - ERR_MSG("pthread_mutex_unlock()", rc); + FAIL_AND_EXIT("pthread_mutex_unlock()", rc); rc = pthread_join(t1, &r1); - if (rc) { - ERR_MSG("pthread_join(t1)", rc); - goto done; - } + if (rc) + FAIL_AND_EXIT("pthread_join(t1)", rc); rc = pthread_join(t2, &r2); - if (rc) { - ERR_MSG("pthread_join(t2)", rc); - goto done; - } + if (rc) + FAIL_AND_EXIT("pthread_join(t2)", rc); rc = pthread_join(t3, &r3); - if (rc) { - ERR_MSG("pthread_join(t3)", rc); - goto done; - } - - /* Threads fail? */ - if ((long)r1 || (long)r2 || (long)r2) - goto done; + if (rc) + FAIL_AND_EXIT("pthread_join(t3)", rc); /* priorities must be high to low */ status = PTS_FAIL; @@ -223,7 +187,6 @@ int main(void) else status = PTS_PASS; -done: if (status == PTS_PASS) printf("Test PASSED\n"); -- 1.7.1 |
From: Jan S. <jst...@re...> - 2013-10-03 11:32:21
|
Test can hang during startup in following scenario: main new thread --------------------------------------------------+------------------------------------- int create_thread(int prio, pthread_t * tid) | ... | pthread_create(tid, &attr, thread_func, NULL);| while (!thread_started) { | | void *thread_func(void *data) | thread_started = 1; | pthread_cond_signal(&cond); pthread_mutex_lock(&c_mutex); | 132: pthread_cond_wait(&cond, &c_mutex); | |65: pthread_mutex_lock(&mutex); | (gdb) bt #0 0x00007fd588808f6d in __lll_lock_wait () from /lib64/libpthread.so.0 #1 0x00007fd588804d31 in _L_lock_790 () from /lib64/libpthread.so.0 #2 0x00007fd588804c37 in pthread_mutex_lock () from /lib64/libpthread.so.0 #3 0x0000000000400bba in thread_func (data=0x0) at ../../../conformance/interfaces/pthread_attr_setschedpolicy/2-1.c:65 #4 0x00007fd588802de3 in start_thread () from /lib64/libpthread.so.0 #5 0x00007fd5885300dd in clone () from /lib64/libc.so.6 (gdb) t 2 (gdb) bt #0 0x00007fd5888066f5 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0 #1 0x0000000000400d9b in create_thread (prio=5, tid=0x7fffdb562678) at ../../../conformance/interfaces/pthread_attr_setschedpolicy/2-1.c:132 #2 0x0000000000400e82 in main () at ../../../conformance/interfaces/pthread_attr_setschedpolicy/2-1.c:174 Fix this by using same c_mutex in thread_func for updating thread_started and signalling cond. Signed-off-by: Jan Stancek <jst...@re...> --- .../interfaces/pthread_attr_setschedpolicy/2-1.c | 20 ++++++++++++-------- 1 files changed, 12 insertions(+), 8 deletions(-) diff --git a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c index 6c471d6..80ce906 100644 --- a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c +++ b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c @@ -56,10 +56,16 @@ static void *thread_func(void *data) if (rc) FAIL_AND_EXIT("pthread_getschedparam()", rc); + rc = pthread_mutex_lock(&c_mutex); + if (rc) + FAIL_AND_EXIT("pthread_mutex_lock()", rc); thread_started = 1; rc = pthread_cond_signal(&cond); if (rc) FAIL_AND_EXIT("pthread_cond_signal()", rc); + rc = pthread_mutex_unlock(&c_mutex); + if (rc) + FAIL_AND_EXIT("pthread_mutex_unlock()", rc); rc = pthread_mutex_lock(&mutex); if (rc) @@ -109,19 +115,17 @@ static int create_thread(int prio, pthread_t * tid) if (rc) FAIL_AND_EXIT("pthread_create()", rc); + rc = pthread_mutex_lock(&c_mutex); + if (rc) + FAIL_AND_EXIT("pthread_mutex_lock()", rc); while (!thread_started) { - rc = pthread_mutex_lock(&c_mutex); - if (rc) - FAIL_AND_EXIT("pthread_mutex_lock()", rc); - rc = pthread_cond_wait(&cond, &c_mutex); if (rc) FAIL_AND_EXIT("pthread_cond_wait()", rc); - - rc = pthread_mutex_unlock(&c_mutex); - if (rc) - FAIL_AND_EXIT("pthread_mutex_unlock()", rc); } + rc = pthread_mutex_unlock(&c_mutex); + if (rc) + FAIL_AND_EXIT("pthread_mutex_unlock()", rc); pthread_attr_destroy(&attr); -- 1.7.1 |
From: <ch...@su...> - 2013-10-03 12:23:23
|
Hi! > Test can hang during startup in following scenario: > > main new thread > --------------------------------------------------+------------------------------------- > int create_thread(int prio, pthread_t * tid) | > ... | > pthread_create(tid, &attr, thread_func, NULL);| > while (!thread_started) { | > | void *thread_func(void *data) > | thread_started = 1; > | pthread_cond_signal(&cond); > pthread_mutex_lock(&c_mutex); | > 132: pthread_cond_wait(&cond, &c_mutex); | > |65: pthread_mutex_lock(&mutex); > | > > (gdb) bt > #0 0x00007fd588808f6d in __lll_lock_wait () from /lib64/libpthread.so.0 > #1 0x00007fd588804d31 in _L_lock_790 () from /lib64/libpthread.so.0 > #2 0x00007fd588804c37 in pthread_mutex_lock () from /lib64/libpthread.so.0 > #3 0x0000000000400bba in thread_func (data=0x0) at ../../../conformance/interfaces/pthread_attr_setschedpolicy/2-1.c:65 > #4 0x00007fd588802de3 in start_thread () from /lib64/libpthread.so.0 > #5 0x00007fd5885300dd in clone () from /lib64/libc.so.6 > (gdb) t 2 > (gdb) bt > #0 0x00007fd5888066f5 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0 > #1 0x0000000000400d9b in create_thread (prio=5, tid=0x7fffdb562678) at ../../../conformance/interfaces/pthread_attr_setschedpolicy/2-1.c:132 > #2 0x0000000000400e82 in main () at ../../../conformance/interfaces/pthread_attr_setschedpolicy/2-1.c:174 > > Fix this by using same c_mutex in thread_func for updating > thread_started and signalling cond. Looks good. -- Cyril Hrubis ch...@su... |
From: Jan S. <jst...@re...> - 2013-10-03 11:32:23
|
Use small sleep for lack of better way to check that all threads are blocked on mutex "mutex". Signed-off-by: Jan Stancek <jst...@re...> --- .../interfaces/pthread_attr_setschedpolicy/2-1.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c index 80ce906..1f8825a 100644 --- a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c +++ b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c @@ -161,6 +161,9 @@ int main(void) if (rc) FAIL_AND_EXIT("create_thread HIGH", rc); + /* give threads a moment so they can block on mutex "mutex" */ + sleep(2); + rc = pthread_mutex_unlock(&mutex); if (rc) FAIL_AND_EXIT("pthread_mutex_unlock()", rc); -- 1.7.1 |
From: Jan S. <jst...@re...> - 2013-10-04 06:47:55
|
To make sure that threads are blocked on mutex, bind all to single CPU. Because they all use SCHED_FIFO policy with main thread having the lowest priority, main will progress only after three created threads block on mutex. Signed-off-by: Jan Stancek <jst...@re...> --- .../interfaces/pthread_attr_setschedpolicy/2-1.c | 14 ++++++++++++++ 1 files changed, 14 insertions(+), 0 deletions(-) diff --git a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c index 80ce906..af8e3e4 100644 --- a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c +++ b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c @@ -20,6 +20,7 @@ * Date: 20/05/2011 */ +#define _GNU_SOURCE #include <stdio.h> #include <string.h> #include <pthread.h> @@ -27,11 +28,13 @@ #include <stdlib.h> #include <errno.h> #include <posixtest.h> +#include <affinity.h> /* Priorities for the threads, must be unique, non-zero, and ordered */ #define PRIO_HIGH 20 #define PRIO_MED 10 #define PRIO_LOW 5 +#define PRIO_MAIN 1 static int priorities[3]; @@ -142,9 +145,20 @@ int main(void) pthread_t t1; pthread_t t2; pthread_t t3; + struct sched_param sp; status = PTS_UNRESOLVED; + + rc = set_affinity(0); + if (rc) + FAIL_AND_EXIT("set_affinity", errno); + + sp.sched_priority = PRIO_MAIN; + rc = pthread_setschedparam(pthread_self(), SCHED_FIFO, &sp); + if (rc) + FAIL_AND_EXIT("pthread_setschedparam()", rc); + rc = pthread_mutex_lock(&mutex); if (rc) FAIL_AND_EXIT("pthread_mutex_lock()", rc); -- 1.7.1 |
From: <ch...@su...> - 2013-10-14 12:00:48
|
Hi! > To make sure that threads are blocked on mutex, bind all to single CPU. > Because they all use SCHED_FIFO policy with main thread having the lowest > priority, main will progress only after three created threads block on > mutex. Looks good. -- Cyril Hrubis ch...@su... |
From: Jan S. <jst...@re...> - 2013-10-17 07:59:49
|
----- Original Message ----- > From: ch...@su... > To: "Jan Stancek" <jst...@re...> > Cc: ltp...@li... > Sent: Monday, 14 October, 2013 2:00:35 PM > Subject: Re: [LTP] [PATCH v2 3/3] pthread_attr_setschedpolicy/2-1.c: bind threads to single CPU > > Hi! > > To make sure that threads are blocked on mutex, bind all to single CPU. > > Because they all use SCHED_FIFO policy with main thread having the lowest > > priority, main will progress only after three created threads block on > > mutex. > > Looks good. Series pushed, regards, Jan > > -- > Cyril Hrubis > ch...@su... > |
From: <ch...@su...> - 2013-10-03 12:02:53
|
Hi! > Remove all gotos and if there's error in any of pthread > functions exit immediately. > > Signed-off-by: Jan Stancek <jst...@re...> Looks good. -- Cyril Hrubis ch...@su... |
From: <ch...@su...> - 2013-10-03 12:38:12
|
Hi! > Use small sleep for lack of better way to check that all threads > are blocked on mutex "mutex". > > Signed-off-by: Jan Stancek <jst...@re...> > --- > .../interfaces/pthread_attr_setschedpolicy/2-1.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c > index 80ce906..1f8825a 100644 > --- a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c > +++ b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c > @@ -161,6 +161,9 @@ int main(void) > if (rc) > FAIL_AND_EXIT("create_thread HIGH", rc); > > + /* give threads a moment so they can block on mutex "mutex" */ > + sleep(2); > + > rc = pthread_mutex_unlock(&mutex); > if (rc) > FAIL_AND_EXIT("pthread_mutex_unlock()", rc); Hmm, so you did hit the small window for race condition between the new thread signals the main thread that it's executed and the next call to the mutex_lock on the tested mutex? I do not like this solution much, but this is not easy to do properly. One posibility is to pinpoint the threads on one cpu via the affinity() interface (open_posix_testsuite/include/affinity.h) then we can wait in the main thread until the thread with lowest priority is executed and safely say that the rest is locked on the mutex allready (as they run with FIFO scheduling). -- Cyril Hrubis ch...@su... |
From: Jan S. <jst...@re...> - 2013-10-03 12:58:22
|
----- Original Message ----- > From: ch...@su... > To: "Jan Stancek" <jst...@re...> > Cc: ltp...@li... > Sent: Thursday, 3 October, 2013 2:38:34 PM > Subject: Re: [LTP] [PATCH 3/3] pthread_attr_setschedpolicy/2-1.c: give threads a moment to block on mutex > > Hi! > > Use small sleep for lack of better way to check that all threads > > are blocked on mutex "mutex". > > > > Signed-off-by: Jan Stancek <jst...@re...> > > --- > > .../interfaces/pthread_attr_setschedpolicy/2-1.c | 3 +++ > > 1 files changed, 3 insertions(+), 0 deletions(-) > > > > diff --git > > a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c > > b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c > > index 80ce906..1f8825a 100644 > > --- > > a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c > > +++ > > b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c > > @@ -161,6 +161,9 @@ int main(void) > > if (rc) > > FAIL_AND_EXIT("create_thread HIGH", rc); > > > > + /* give threads a moment so they can block on mutex "mutex" */ > > + sleep(2); > > + > > rc = pthread_mutex_unlock(&mutex); > > if (rc) > > FAIL_AND_EXIT("pthread_mutex_unlock()", rc); > > Hmm, so you did hit the small window for race condition between the new > thread signals the main thread that it's executed and the next call to > the mutex_lock on the tested mutex? Yes, I'm assuming this is reason why I see it sporadically failing on different distros/kernels. I see it happening the most on IBM z/VM (s390) guests which have overcommitted resources, which affects scheduling. It takes longer, but I could trigger it on x86_64 too. > > I do not like this solution much, but this is not easy to do properly. > One posibility is to pinpoint the threads on one cpu via the affinity() > interface (open_posix_testsuite/include/affinity.h) then we can wait in > the main thread until the thread with lowest priority is executed and > safely say that the rest is locked on the mutex allready (as they run > with FIFO scheduling). I was considering this too, but there are some problems: 1. pthread_setaffinity_np is not portable / sched_setaffinity is Linux only 2. linux default sched_rt_runtime_us gives 0.05s to be used by SCHED_OTHER (non-RT tasks) (Documentation/scheduler/sched-rt-group.txt) If we set also main thread to use SCHED_FIFO, then this shouldn't be problem. If you are OK with using pthread_setaffinity_np(), I can add that. Regards, Jan > > -- > Cyril Hrubis > ch...@su... > |
From: Jan S. <jst...@re...> - 2013-10-03 13:02:41
|
----- Original Message ----- > From: "Jan Stancek" <jst...@re...> > To: ch...@su... > Cc: ltp...@li... > Sent: Thursday, 3 October, 2013 2:58:14 PM > Subject: Re: [LTP] [PATCH 3/3] pthread_attr_setschedpolicy/2-1.c: give threads a moment to block on mutex > > > > ----- Original Message ----- > > From: ch...@su... > > To: "Jan Stancek" <jst...@re...> > > Cc: ltp...@li... > > Sent: Thursday, 3 October, 2013 2:38:34 PM > > Subject: Re: [LTP] [PATCH 3/3] pthread_attr_setschedpolicy/2-1.c: give > > threads a moment to block on mutex > > > > Hi! > > > Use small sleep for lack of better way to check that all threads > > > are blocked on mutex "mutex". > > > > > > Signed-off-by: Jan Stancek <jst...@re...> > > > --- > > > .../interfaces/pthread_attr_setschedpolicy/2-1.c | 3 +++ > > > 1 files changed, 3 insertions(+), 0 deletions(-) > > > > > > diff --git > > > a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c > > > b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c > > > index 80ce906..1f8825a 100644 > > > --- > > > a/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c > > > +++ > > > b/testcases/open_posix_testsuite/conformance/interfaces/pthread_attr_setschedpolicy/2-1.c > > > @@ -161,6 +161,9 @@ int main(void) > > > if (rc) > > > FAIL_AND_EXIT("create_thread HIGH", rc); > > > > > > + /* give threads a moment so they can block on mutex "mutex" */ > > > + sleep(2); > > > + > > > rc = pthread_mutex_unlock(&mutex); > > > if (rc) > > > FAIL_AND_EXIT("pthread_mutex_unlock()", rc); > > > > Hmm, so you did hit the small window for race condition between the new > > thread signals the main thread that it's executed and the next call to > > the mutex_lock on the tested mutex? > > Yes, I'm assuming this is reason why I see it sporadically failing on > different distros/kernels. I see it happening the most on IBM z/VM (s390) > guests which have overcommitted resources, which affects scheduling. > > It takes longer, but I could trigger it on x86_64 too. > > > > > I do not like this solution much, but this is not easy to do properly. > > One posibility is to pinpoint the threads on one cpu via the affinity() > > interface (open_posix_testsuite/include/affinity.h) then we can wait in > > the main thread until the thread with lowest priority is executed and > > safely say that the rest is locked on the mutex allready (as they run > > with FIFO scheduling). > > I was considering this too, but there are some problems: > > 1. pthread_setaffinity_np is not portable / sched_setaffinity is Linux only > 2. linux default sched_rt_runtime_us gives 0.05s to be used by > SCHED_OTHER (non-RT tasks) (Documentation/scheduler/sched-rt-group.txt) > If we set also main thread to use SCHED_FIFO, then this shouldn't be > problem. > > If you are OK with using pthread_setaffinity_np(), I can add that. Sorry, I overlooked you already gave example to function in affinity.h. I'll use this one. Regards, Jan > > Regards, > Jan > > > > > -- > > Cyril Hrubis > > ch...@su... > > > > ------------------------------------------------------------------------------ > October Webinars: Code for Performance > Free Intel webinars can help you accelerate application performance. > Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from > the latest Intel processors and coprocessors. See abstracts and register > > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk > _______________________________________________ > Ltp-list mailing list > Ltp...@li... > https://lists.sourceforge.net/lists/listinfo/ltp-list > |
From: <ch...@su...> - 2013-10-03 13:12:42
|
Hi! > > Hmm, so you did hit the small window for race condition between the new > > thread signals the main thread that it's executed and the next call to > > the mutex_lock on the tested mutex? > > Yes, I'm assuming this is reason why I see it sporadically failing on > different distros/kernels. I see it happening the most on IBM z/VM (s390) > guests which have overcommitted resources, which affects scheduling. > > It takes longer, but I could trigger it on x86_64 too. I think that I know where the problem may come from. We are starting the threads in reverse order by priority, so the lowest one can actually be preempted by the higher priority one before the lock is taken, which makes sense. > > I do not like this solution much, but this is not easy to do properly. > > One posibility is to pinpoint the threads on one cpu via the affinity() > > interface (open_posix_testsuite/include/affinity.h) then we can wait in > > the main thread until the thread with lowest priority is executed and > > safely say that the rest is locked on the mutex allready (as they run > > with FIFO scheduling). > > I was considering this too, but there are some problems: > > 1. pthread_setaffinity_np is not portable / sched_setaffinity is Linux only This is the reason we have the open_posix_testsuite/include/affinity.h, it's not portable but some test cannot be written without it and it's implemented on most POSIX OSes, so we keep the unportable chunks in one place. > 2. linux default sched_rt_runtime_us gives 0.05s to be used by > SCHED_OTHER (non-RT tasks) (Documentation/scheduler/sched-rt-group.txt) > If we set also main thread to use SCHED_FIFO, then this shouldn't be problem. That shouldn't be much of problem, the main thread would pick up once the realtime threads are locked on mutexes/cond vars. Or am I mistaken here? -- Cyril Hrubis ch...@su... |
From: Jan S. <jst...@re...> - 2013-10-03 13:26:14
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----- Original Message ----- > From: ch...@su... > To: "Jan Stancek" <jst...@re...> > Cc: ltp...@li... > Sent: Thursday, 3 October, 2013 3:13:06 PM > Subject: Re: [LTP] [PATCH 3/3] pthread_attr_setschedpolicy/2-1.c: give threads a moment to block on mutex > > Hi! > > > Hmm, so you did hit the small window for race condition between the new > > > thread signals the main thread that it's executed and the next call to > > > the mutex_lock on the tested mutex? > > > > Yes, I'm assuming this is reason why I see it sporadically failing on > > different distros/kernels. I see it happening the most on IBM z/VM (s390) > > guests which have overcommitted resources, which affects scheduling. > > > > It takes longer, but I could trigger it on x86_64 too. > > I think that I know where the problem may come from. We are starting the > threads in reverse order by priority, so the lowest one can actually be > preempted by the higher priority one before the lock is taken, which > makes sense. > > > > I do not like this solution much, but this is not easy to do properly. > > > One posibility is to pinpoint the threads on one cpu via the affinity() > > > interface (open_posix_testsuite/include/affinity.h) then we can wait in > > > the main thread until the thread with lowest priority is executed and > > > safely say that the rest is locked on the mutex allready (as they run > > > with FIFO scheduling). > > > > I was considering this too, but there are some problems: > > > > 1. pthread_setaffinity_np is not portable / sched_setaffinity is Linux only > > This is the reason we have the open_posix_testsuite/include/affinity.h, > it's not portable but some test cannot be written without it and it's > implemented on most POSIX OSes, so we keep the unportable chunks in one > place. > > > 2. linux default sched_rt_runtime_us gives 0.05s to be used by > > SCHED_OTHER (non-RT tasks) (Documentation/scheduler/sched-rt-group.txt) > > If we set also main thread to use SCHED_FIFO, then this shouldn't be > > problem. > > That shouldn't be much of problem, the main thread would pick up once > the realtime threads are locked on mutexes/cond vars. Or am I mistaken > here? (assuming all threads are bound to single CPU) That's true, but (the way I understand it) non-rt main thread can also run when scheduler thinks that RT processes are monopolizing CPU for too long. So you can't be sure that thread is actually on "mutex". thread_func(): pthread_mutex_lock(&c_mutex); pthread_cond_signal(&cond); pthread_mutex_unlock(&c_mutex); --> here scheduler decides it's time to give a chance to non-rt threads and runs main thread, condition was already signalled so main thinks thread is already blocking on mutex pthread_mutex_lock(&mutex); If we set SCHED_FIFO also on main thread with lowest priority, then it shouldn't run regardless of value in sched_rt_runtime_us. Regards, Jan > > -- > Cyril Hrubis > ch...@su... > |
From: <ch...@su...> - 2013-10-03 13:46:13
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Hi! > > > 2. linux default sched_rt_runtime_us gives 0.05s to be used by > > > SCHED_OTHER (non-RT tasks) (Documentation/scheduler/sched-rt-group.txt) > > > If we set also main thread to use SCHED_FIFO, then this shouldn't be > > > problem. > > > > That shouldn't be much of problem, the main thread would pick up once > > the realtime threads are locked on mutexes/cond vars. Or am I mistaken > > here? > > (assuming all threads are bound to single CPU) > That's true, but (the way I understand it) non-rt main thread can also run > when scheduler thinks that RT processes are monopolizing CPU for too long. As I understand it, it's a anti lockup measure so if the kernel detects that realtime threads has been running for nearly a second in a row it stops the execution and schedules some other threads. But that shouldn't be the case here. > So you can't be sure that thread is actually on "mutex". > > thread_func(): > pthread_mutex_lock(&c_mutex); > pthread_cond_signal(&cond); > pthread_mutex_unlock(&c_mutex); > --> here scheduler decides it's time to give a chance to non-rt threads > and runs main thread, condition was already signalled so main thinks > thread is already blocking on mutex > pthread_mutex_lock(&mutex); > > If we set SCHED_FIFO also on main thread with lowest priority, then > it shouldn't run regardless of value in sched_rt_runtime_us. That is why I said that we have to wait for the lowest priority thread to run. Giving the main thread even lower priority is a way of doing that. -- Cyril Hrubis ch...@su... |