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List: busybox
Subject: [PATCH] chrt: support for musl C library
From: Christian Eggers <ceggers () arri ! de>
Date: 2020-09-11 15:45:38
Message-ID: 20200911154538.28451-1-ceggers () arri ! de
[Download RAW message or body]
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>
---
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 [...]" */
--
Christian Eggers
Embedded software developer
Arnold & Richter Cine Technik GmbH & Co. Betriebs KG
Sitz: Muenchen - Registergericht: Amtsgericht Muenchen - Handelsregisternummer: HRA \
57918 Persoenlich haftender Gesellschafter: Arnold & Richter Cine Technik GmbH
Sitz: Muenchen - Registergericht: Amtsgericht Muenchen - Handelsregisternummer: HRB \
54477
Geschaeftsfuehrer: Dr. Michael Neuhaeuser; Stephan Schenk; Walter Trauninger; Markus \
Zeiler
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