From 93332ebdcd54b0e0c0e86bced537cc96247bc1f1 Mon Sep 17 00:00:00 2001 From: Hauke Mehrtens Date: Sat, 23 Jan 2016 16:23:09 +0100 Subject: [PATCH 2/2] mips: add vdso support vdso support is available on mips starting with kernel 4.4, see kernel commit a7f4df4e21 "MIPS: VDSO: Add implementations of gettimeofday() and clock_gettime()" for details. In Linux kernel 4.4.0 the mips code returns -ENOSYS in case it can not handle the vdso call and assumes the libc will call the original syscall in this case. Handle this case in musl. Currently Linux kernel 4.4.0 handles the following types: CLOCK_REALTIME_COARSE, CLOCK_MONOTONIC_COARSE, CLOCK_REALTIME and CLOCK_MONOTONIC. These are some measurements of calling clock_gettime(CLOCK_MONOTONIC, &tp); 1.000.000 times. without vdso: root@OpenWrt:/# time ./vdso-test real 0m 0.95s user 0m 0.24s sys 0m 0.70s with vdso: root@OpenWrt:/# time /usr/bin/vdso-test real 0m 0.35s user 0m 0.34s sys 0m 0.00s Signed-off-by: Hauke Mehrtens --- arch/mips/syscall_arch.h | 4 ++++ src/time/clock_gettime.c | 12 +++++++++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/mips/syscall_arch.h b/arch/mips/syscall_arch.h index e74e0ad..39c0ea3 100644 --- a/arch/mips/syscall_arch.h +++ b/arch/mips/syscall_arch.h @@ -161,3 +161,7 @@ static inline long __syscall6(long n, long a, long b, long c, long d, long e, lo if (n == SYS_fstatat) __stat_fix(c); return r2; } + +#define VDSO_USEFUL +#define VDSO_CGT_SYM "__vdso_clock_gettime" +#define VDSO_CGT_VER "LINUX_2.6" diff --git a/src/time/clock_gettime.c b/src/time/clock_gettime.c index 1572de0..dba99ff 100644 --- a/src/time/clock_gettime.c +++ b/src/time/clock_gettime.c @@ -26,13 +26,23 @@ void *__vdsosym(const char *, const char *); int __clock_gettime(clockid_t clk, struct timespec *ts) { #ifdef VDSO_CGT_SYM + int ret; static int (*volatile cgt)(clockid_t, struct timespec *); if (!cgt) { void *f = __vdsosym(VDSO_CGT_VER, VDSO_CGT_SYM); if (!f) f = (void *)sc_clock_gettime; a_cas_p(&cgt, 0, f); } - return cgt(clk, ts); + ret = cgt(clk, ts); + + /* + * mips in linux kernel 4.4.0 returns -ENOSYS if it can not + * handle the syscall in vdso, the original syscall should be + * called by the libc in such a case. + */ + if (ret == -ENOSYS) + return sc_clock_gettime(clk, ts); + return ret; #else return sc_clock_gettime(clk, ts); #endif -- 2.7.0.rc3