As mentioned in [1], the testcase hangs on -rt kernel, because alarm(2) will never fire. The testcase runs with FIFO scheduling of higher priority than ksoftirqd.
This patch changes testcase in following way: 1. In good case, where child process preempts parent, child is able to detect this condition and terminate. 2. In bad case, where preemption fails, testcase doesn't rely on softirq (alarm), but hrtimer (time). 3. removes unnecessary sleep [1] https://lkml.org/lkml/2006/1/10/481 Reported-by: Jiri Kastner <jkast...@redhat.com> Signed-off-by: Jan Stancek <jstan...@redhat.com> --- .../conformance/interfaces/sched_setparam/9-1.c | 53 +++++++++++++++------- 1 file changed, 37 insertions(+), 16 deletions(-) Changes in v2: - refined comment - replace exit() with pause(), so kill_children() has pid to kill diff --git a/testcases/open_posix_testsuite/conformance/interfaces/sched_setparam/9-1.c b/testcases/open_posix_testsuite/conformance/interfaces/sched_setparam/9-1.c index ed90cee..48ef1b0 100644 --- a/testcases/open_posix_testsuite/conformance/interfaces/sched_setparam/9-1.c +++ b/testcases/open_posix_testsuite/conformance/interfaces/sched_setparam/9-1.c @@ -31,14 +31,15 @@ * not, the test fail. */ #define _GNU_SOURCE +#include <errno.h> #include <sched.h> #include <stdio.h> #include <signal.h> +#include <stdlib.h> #include <sys/ipc.h> #include <sys/shm.h> +#include <time.h> #include <unistd.h> -#include <stdlib.h> -#include <errno.h> #include "posixtest.h" #include "affinity.h" @@ -55,6 +56,7 @@ static int nb_cpu; static int *shmptr; +static int mean_prio; static int get_ncpu(void) { @@ -85,6 +87,7 @@ static int get_ncpu(void) static void child_process(void) { struct sched_param param; + time_t t1, t2; param.sched_priority = sched_get_priority_max(SCHED_FIFO); if (sched_setparam(getpid(), ¶m) != 0) { @@ -92,20 +95,40 @@ static void child_process(void) return; } - /* to avoid blocking */ - alarm(2); - while (1) ; + t1 = time(NULL); + do { + t2 = time(NULL); + } while (difftime(t2, t1) <= 2); } static void test_process(void) { - /* to avoid blocking */ - alarm(2); - - while (1) { - (*shmptr)++; + struct sched_param param; + time_t t1, t2; + + t1 = time(NULL); + do { + sched_getparam(getpid(), ¶m); + (*shmptr) = param.sched_priority; + /* if we can see that our priority has changed + * that means we preempted parent, so we are done */ + if ((*shmptr) == mean_prio) + break; + + t2 = time(NULL); + /* OS-es supporting set_affinity(), like Linux, will + * have only one parent and child process competing + * for same CPU. Since code path in parent does not + * block between fork() and sched_setparam(), child + * should run only after parent boosted its priority. + * Situation on other OS-es is a bit less predictable, + * as these will spawn ncpu-1 children, which run at max + * priority and could (though unlikely) preempt parent. + * Rather than risking deadlock, keep the sched_yield() + * call in loop as it is harmless. */ sched_yield(); - } + } while (difftime(t2, t1) <= 2); + pause(); } static void kill_children(int *child_pid) @@ -133,6 +156,8 @@ int main(void) nb_cpu = 1; } + mean_prio = (sched_get_priority_min(SCHED_FIFO) + + sched_get_priority_max(SCHED_FIFO)) / 2; child_pid = malloc(nb_cpu * sizeof(int)); key = ftok("conformance/interfaces/sched_setparam/9-1.c", 1234); @@ -194,11 +219,7 @@ int main(void) return PTS_UNRESOLVED; } - sleep(1); - - param.sched_priority = (sched_get_priority_min(SCHED_FIFO) + - sched_get_priority_max(SCHED_FIFO)) / 2; - + param.sched_priority = mean_prio; oldcount = *shmptr; if (sched_setparam(child_pid[i], ¶m) != 0) { perror("An error occurs when calling sched_setparam()"); -- 1.8.3.1 ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ Ltp-list mailing list Ltp-list@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ltp-list
