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chrt: support for musl C library

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musl "implements" several sched_xxx() functions by returning ENOSYS. As
an alternative, either pthread_(g|s)etschedparam() or direct syscalls
can be used.

References: https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/commit/schedutils/chrt.c?id=fcc3078754291d2f5121797eb91b364f8e24b2f1
References: http://git.musl-libc.org/cgit/musl/commit/src/sched/sched_setscheduler.c?id=1e21e78bf7a5c24c217446d8760be7b7188711c2
Signed-off-by: Christian Eggers <ceggers@arri.de>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Christian Eggers
2020-11-15 20:25:09 +01:00
committed by Denys Vlasenko
parent 64981b4c8e
commit 89f063b900
1 changed files with 32 additions and 2 deletions
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34
util-linux/chrt.c
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@@ -39,6 +39,17 @@
# define SCHED_IDLE 5
#endif
//musl has no __MUSL__ or similar define to check for,
//but its <sys/types.h> has these lines:
// #define __NEED_fsblkcnt_t
// #define __NEED_fsfilcnt_t
#if defined(__linux__) && defined(__NEED_fsblkcnt_t) && defined(__NEED_fsfilcnt_t)
# define LIBC_IS_MUSL 1
# include <sys/syscall.h>
#else
# define LIBC_IS_MUSL 0
#endif
static const char *policy_name(int pol)
{
if (pol > 6)
@@ -85,6 +96,7 @@ int chrt_main(int argc UNUSED_PARAM, char **argv)
char *priority = priority; /* for compiler */
const char *current_new;
int policy = SCHED_RR;
int ret;
opt = getopt32(argv, "^"
"+" "mprfobi"
@@ -132,7 +144,15 @@ int chrt_main(int argc UNUSED_PARAM, char **argv)
if (opt & OPT_p) {
int pol;
print_rt_info:
#if LIBC_IS_MUSL
/* musl libc returns ENOSYS for its sched_getscheduler library
* function, because the sched_getscheduler Linux kernel system call
* does not conform to Posix; so we use the system call directly
*/
pol = syscall(SYS_sched_getscheduler, pid);
#else
pol = sched_getscheduler(pid);
#endif
if (pol < 0)
bb_perror_msg_and_die("can't %cet pid %u's policy", 'g', (int)pid);
#ifdef SCHED_RESET_ON_FORK
@@ -149,7 +169,12 @@ int chrt_main(int argc UNUSED_PARAM, char **argv)
printf("pid %u's %s scheduling policy: SCHED_%s\n",
pid, current_new, policy_name(pol)
);
if (sched_getparam(pid, &sp))
#if LIBC_IS_MUSL
ret = syscall(SYS_sched_getparam, pid, &sp);
#else
ret = sched_getparam(pid, &sp);
#endif
if (ret)
bb_perror_msg_and_die("can't get pid %u's attributes", (int)pid);
printf("pid %u's %s scheduling priority: %d\n",
(int)pid, current_new, sp.sched_priority
@@ -168,7 +193,12 @@ int chrt_main(int argc UNUSED_PARAM, char **argv)
sched_get_priority_min(policy), sched_get_priority_max(policy)
);
if (sched_setscheduler(pid, policy, &sp) < 0)
#if LIBC_IS_MUSL
ret = syscall(SYS_sched_setscheduler, pid, policy, &sp);
#else
ret = sched_setscheduler(pid, policy, &sp);
#endif
if (ret)
bb_perror_msg_and_die("can't %cet pid %u's policy", 's', (int)pid);
if (!argv[0]) /* "-p PRIO PID [...]" */