On Fri, Sep 11, 2020 at 6:18 PM Christian Eggers <cegg...@arri.de> wrote: > 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 <cegg...@arri.de> > --- > util-linux/chrt.c | 31 +++++++++++++++++++++++++++++-- > 1 file changed, 29 insertions(+), 2 deletions(-) > > diff --git a/util-linux/chrt.c b/util-linux/chrt.c > index 4dd78dabf..e465d7cec 100644 > --- a/util-linux/chrt.c > +++ b/util-linux/chrt.c > @@ -34,6 +34,9 @@ > //usage: "You need CAP_SYS_NICE privileges to set scheduling > attributes of a process" > > #include <sched.h> > +#if defined (__linux__) > +# include <sys/syscall.h> > +#endif > #include "libbb.h" > #ifndef SCHED_IDLE > # define SCHED_IDLE 5 > @@ -85,6 +88,7 @@ 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 +136,15 @@ int chrt_main(int argc UNUSED_PARAM, char **argv) > if (opt & OPT_p) { > int pol; > print_rt_info: > +#if defined (__linux__) && defined(SYS_sched_getscheduler) > + /* 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 +161,12 @@ 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 defined (__linux__) && defined(SYS_sched_getparam) > + 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 +185,17 @@ 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 defined (__linux__) && defined(SYS_sched_setscheduler) > + /* musl libc returns ENOSYS for its sched_setscheduler library > + * function, because the sched_setscheduler Linux kernel system call > + * does not conform to Posix; so we use the system call directly > + */ > + ret = syscall(SYS_sched_setscheduler, pid, policy, &sp); > +#else > + ret = sched_setscheduler(pid, policy, &sp); > +#endif > + > + if (ret < 0) > bb_perror_msg_and_die("can't %cet pid %u's policy", 's', > (int)pid); > > if (!argv[0]) /* "-p PRIO PID [...]" */
I looked at it several times, but this looks not so good. These direct syscalls are less maintainable. OTOH... by the looks of it, there is no alternative? I'll probably apply it. _______________________________________________ busybox mailing list busybox@busybox.net http://lists.busybox.net/mailman/listinfo/busybox
