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chrt: add fallback to be usable on kernels without sched_{get,set}attr 

We have fallback for compilation with/without proper glibc and kernel
headers, but it's not enough, because people can switch between
kernels with and without the syscalls. (For example RT kernels for
RHEL/CentOS).

Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1353340
Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2016-07-11 15:33:46 +02:00
parent 2cad2b32ff
commit 6f27e449a9
1 changed files with 43 additions and 8 deletions
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51
schedutils/chrt.c
View File

@ -58,11 +58,19 @@
# define SCHED_FLAG_RESET_ON_FORK 0x01
#endif
#if defined (__linux__) && !defined(HAVE_SCHED_SETATTR)
# include <sys/syscall.h>
#endif
/* usable kernel-headers, but old glibc-headers */
#if defined (__linux__) && !defined(SYS_sched_setattr) && defined(__NR_sched_setattr)
# define SYS_sched_setattr __NR_sched_setattr
#endif
#if defined (__linux__) && !defined(SYS_sched_getattr) && defined(__NR_sched_getattr)
# define SYS_sched_getattr __NR_sched_getattr
#endif
#if defined (__linux__) && !defined(HAVE_SCHED_SETATTR) && defined(SYS_sched_setattr)
# define HAVE_SCHED_SETATTR
@ -207,12 +215,20 @@ static void show_sched_pid_info(struct chrt_ctl *ctl, pid_t pid)
if (!pid)
pid = getpid();
errno = 0;
/*
* New way
*/
#ifdef HAVE_SCHED_SETATTR
{
struct sched_attr sa;
if (sched_getattr(pid, &sa, sizeof(sa), 0) != 0)
if (sched_getattr(pid, &sa, sizeof(sa), 0) != 0) {
if (errno == ENOSYS)
goto fallback;
err(EXIT_FAILURE, _("failed to get pid %d's policy"), pid);
}
policy = sa.sched_policy;
prio = sa.sched_priority;
@ -221,8 +237,13 @@ static void show_sched_pid_info(struct chrt_ctl *ctl, pid_t pid)
runtime = sa.sched_runtime;
period = sa.sched_period;
}
#else /* !HAVE_SCHED_SETATTR */
{
#endif
/*
* Old way
*/
fallback:
if (errno == ENOSYS) {
struct sched_param sp;
policy = sched_getscheduler(pid);
@ -238,7 +259,6 @@ static void show_sched_pid_info(struct chrt_ctl *ctl, pid_t pid)
reset_on_fork = 1;
# endif
}
#endif /* !HAVE_SCHED_SETATTR */
if (ctl->altered)
printf(_("pid %d's new scheduling policy: %s"), pid, get_policy_name(policy));
@ -315,8 +335,7 @@ static void show_min_max(void)
}
}
#ifndef HAVE_SCHED_SETATTR
static int set_sched_one(struct chrt_ctl *ctl, pid_t pid)
static int set_sched_one_by_setscheduler(struct chrt_ctl *ctl, pid_t pid)
{
struct sched_param sp = { .sched_priority = ctl->priority };
int policy = ctl->policy;
@ -328,6 +347,13 @@ static int set_sched_one(struct chrt_ctl *ctl, pid_t pid)
return sched_setscheduler(pid, policy, &sp);
}
#ifndef HAVE_SCHED_SETATTR
static int set_sched_one(struct chrt_ctl *ctl, pid_t pid)
{
return set_sched_one_by_setscheduler(ctl, pid);
}
#else /* !HAVE_SCHED_SETATTR */
static int set_sched_one(struct chrt_ctl *ctl, pid_t pid)
{
@ -340,11 +366,20 @@ static int set_sched_one(struct chrt_ctl *ctl, pid_t pid)
.sched_period = ctl->period,
.sched_deadline = ctl->deadline
};
int rc;
# ifdef SCHED_RESET_ON_FORK
if (ctl->reset_on_fork)
sa.sched_flags |= SCHED_RESET_ON_FORK;
# endif
return sched_setattr(pid, &sa, 0);
errno = 0;
rc = sched_setattr(pid, &sa, 0);
if (rc != 0 && errno == ENOSYS && ctl->policy != SCHED_DEADLINE)
/* fallback -- build with new kernel/libc, but executed on old kernels */
rc = set_sched_one_by_setscheduler(ctl, pid);
return rc;
}
#endif /* HAVE_SCHED_SETATTR */