Hi!
> 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 | 48
> ++++++++++++++--------
> 1 file changed, 32 insertions(+), 16 deletions(-)
>
> 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..354e03e 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 +95,33 @@ 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);
> }
Have you tested this code with dummy set_affinity()? Because on Linux
this doesn't get called at all.
> 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);
> + /* immediately after parent forks us, we has same
> + * priority and compete with parent for same CPU,
> + * give parent chance to run and boost our priority */
> sched_yield();
Hmm, is this the case? Because the main thread should continue to run
until blocked and without the sleep(1) in the main() there is nothing
that could block the parent process between the fork and the priority
boost. Or am I mistaken?
> - }
> + } while (difftime(t2, t1) <= 2);
> + exit(0);
> }
>
> static void kill_children(int *child_pid)
> @@ -133,6 +149,8 @@ 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 +212,9 @@ int main(void)
> return PTS_UNRESOLVED;
> }
>
> - sleep(1);
> -
> - param.sched_priority = (sched_get_priority_min(SCHED_FIFO) +
> - sched_get_priority_max(SCHED_FIFO)) / 2;
> -
> + /* parent runs, which means test_process() gave up cpu,
> + * boost its priority and check it preempted parent */
> + param.sched_priority = mean_prio;
> oldcount = *shmptr;
Shouldn't we rather initialize the shmptr to some known value (!=
mean_prio) now?
> if (sched_setparam(child_pid[i], ¶m) != 0) {
> perror("An error occurs when calling sched_setparam()");
> --
> 1.8.3.1
>
>
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--
Cyril Hrubis
chru...@suse.cz
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