Hi there,
This patch tells chrt utility to uses syscall() instead calling
sched_{g,s}etscheduler() that are provided by libc. Some libc,
e.g. musl does not fully implement the scheduler functions.
Below is the bloat-o-meter output and the patch for 1_31_stable
branch.
Kind Regards,
Fryderyk
$ ./scripts/bloat-o-meter busybox_unstripped.1_31_stable
busybox_unstripped.1_31_chrt_patch
function old new delta
chrt_main 544 586 +42
show_min_max 100 116 +16
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 58/0) Total: 58 bytes
---
util-linux/chrt.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 60 insertions(+), 6 deletions(-)
diff --git a/util-linux/chrt.c b/util-linux/chrt.c
index 4dd78dabf..5c25a23a9 100644
--- a/util-linux/chrt.c
+++ b/util-linux/chrt.c
@@ -12,6 +12,20 @@
//config: Manipulate real-time attributes of a process.
//config: This requires sched_{g,s}etparam support in your libc.
+//config:config FEATURE_CHRT_OWN_SCHED_SYSCALLS
+//config: bool "Use scheduler syscalls directly"
+//config: default n
+//config: depends on CHRT
+//config: help
+//config: Some libc libraries (e.g. musl) do not provide
sched_{g,s}etscheduler
+//config: and sched_{g,s}etparam syscalls. That pretty much renders the
chrt
+//config: utility useless. This feature tells chrt not to rely on libc
and use
+//config: syscall function directly.
+//config:
+//config: If you use a libc that does not have those syscalls say 'y'
here,
+//config: otherwise say 'n'.
+//config:
+
//applet:IF_CHRT(APPLET_NOEXEC(chrt, chrt, BB_DIR_USR_BIN, BB_SUID_DROP, chrt))
//kbuild:lib-$(CONFIG_CHRT) += chrt.o
@@ -35,6 +49,46 @@
#include <sched.h>
#include "libbb.h"
+
+#if ENABLE_FEATURE_CHRT_OWN_SCHED_SYSCALLS
+
+#include <syscall.h>
+
+static inline int bb_sched_setscheduler(int pid, int policy, const
struct sched_param *p)
+{
+ return syscall(SYS_sched_setscheduler, pid, policy, p);
+}
+
+static inline int bb_sched_getscheduler(int pid)
+{
+ return syscall(SYS_sched_getscheduler, pid);
+}
+
+static inline int bb_sched_getparam(int pid, struct sched_param *p)
+{
+ return syscall(SYS_sched_getparam, pid, p);
+}
+
+static inline int bb_sched_get_priority_max(int policy)
+{
+ return syscall(SYS_sched_get_priority_max, policy);
+}
+
+static inline int bb_sched_get_priority_min(int policy)
+{
+ return syscall(SYS_sched_get_priority_min, policy);
+}
+
+#else /* ! ENABLE_FEATURE_CHRT_OWN_SCHED_SYSCALLS */
+
+#define bb_sched_getscheduler sched_getscheduler
+#define bb_sched_setscheduler sched_setscheduler
+#define bb_sched_getparam sched_getparam
+#define bb_sched_get_priority_max sched_get_priority_max
+#define bb_sched_get_priority_min sched_get_priority_min
+
+#endif /* ENABLE_FEATURE_CHRT_OWN_SCHED_SYSCALLS */
+
#ifndef SCHED_IDLE
# define SCHED_IDLE 5
#endif
@@ -60,8 +114,8 @@ static void show_min_max(int pol)
const char *fmt = "SCHED_%s min/max priority\t: %u/%u\n";
int max, min;
- max = sched_get_priority_max(pol);
- min = sched_get_priority_min(pol);
+ max = bb_sched_get_priority_max(pol);
+ min = bb_sched_get_priority_min(pol);
if ((max|min) < 0)
fmt = "SCHED_%s not supported\n";
printf(fmt, policy_name(pol), min, max);
@@ -132,7 +186,7 @@ int chrt_main(int argc UNUSED_PARAM, char **argv)
if (opt & OPT_p) {
int pol;
print_rt_info:
- pol = sched_getscheduler(pid);
+ pol = bb_sched_getscheduler(pid);
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 +203,7 @@ 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 (bb_sched_getparam(pid, &sp))
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
@@ -165,10 +219,10 @@ int chrt_main(int argc UNUSED_PARAM, char **argv)
}
sp.sched_priority = xstrtou_range(priority, 0,
- sched_get_priority_min(policy), sched_get_priority_max(policy)
+ bb_sched_get_priority_min(policy),
bb_sched_get_priority_max(policy)
);
- if (sched_setscheduler(pid, policy, &sp) < 0)
+ if (bb_sched_setscheduler(pid, policy, &sp) < 0)
bb_perror_msg_and_die("can't %cet pid %u's policy", 's',
(int)pid);
if (!argv[0]) /* "-p PRIO PID [...]" */
--
2.16.4
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