chrt: support for musl C library
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>
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@ -39,6 +39,17 @@
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# define SCHED_IDLE 5
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#endif
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//musl has no __MUSL__ or similar define to check for,
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//but its <sys/types.h> has these lines:
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// #define __NEED_fsblkcnt_t
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// #define __NEED_fsfilcnt_t
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#if defined(__linux__) && defined(__NEED_fsblkcnt_t) && defined(__NEED_fsfilcnt_t)
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# define LIBC_IS_MUSL 1
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# include <sys/syscall.h>
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#else
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# define LIBC_IS_MUSL 0
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#endif
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static const char *policy_name(int pol)
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{
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if (pol > 6)
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@ -85,6 +96,7 @@ int chrt_main(int argc UNUSED_PARAM, char **argv)
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char *priority = priority; /* for compiler */
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const char *current_new;
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int policy = SCHED_RR;
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int ret;
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opt = getopt32(argv, "^"
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"+" "mprfobi"
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@ -132,7 +144,15 @@ int chrt_main(int argc UNUSED_PARAM, char **argv)
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if (opt & OPT_p) {
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int pol;
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print_rt_info:
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#if LIBC_IS_MUSL
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/* musl libc returns ENOSYS for its sched_getscheduler library
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* function, because the sched_getscheduler Linux kernel system call
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* does not conform to Posix; so we use the system call directly
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*/
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pol = syscall(SYS_sched_getscheduler, pid);
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#else
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pol = sched_getscheduler(pid);
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#endif
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if (pol < 0)
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bb_perror_msg_and_die("can't %cet pid %u's policy", 'g', (int)pid);
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#ifdef SCHED_RESET_ON_FORK
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@ -149,7 +169,12 @@ int chrt_main(int argc UNUSED_PARAM, char **argv)
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printf("pid %u's %s scheduling policy: SCHED_%s\n",
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pid, current_new, policy_name(pol)
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);
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if (sched_getparam(pid, &sp))
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#if LIBC_IS_MUSL
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ret = syscall(SYS_sched_getparam, pid, &sp);
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#else
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ret = sched_getparam(pid, &sp);
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#endif
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if (ret)
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bb_perror_msg_and_die("can't get pid %u's attributes", (int)pid);
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printf("pid %u's %s scheduling priority: %d\n",
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(int)pid, current_new, sp.sched_priority
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@ -168,7 +193,12 @@ int chrt_main(int argc UNUSED_PARAM, char **argv)
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sched_get_priority_min(policy), sched_get_priority_max(policy)
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);
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if (sched_setscheduler(pid, policy, &sp) < 0)
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#if LIBC_IS_MUSL
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ret = syscall(SYS_sched_setscheduler, pid, policy, &sp);
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#else
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ret = sched_setscheduler(pid, policy, &sp);
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#endif
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if (ret)
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bb_perror_msg_and_die("can't %cet pid %u's policy", 's', (int)pid);
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if (!argv[0]) /* "-p PRIO PID [...]" */
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