Adhemerval Zanella a9091a1244 linux: Optimize fallback 32-bit clock_gettime ... This patch avoid probing the __NR_clock_getttime64 syscall each time __clock_gettime64 is issued on a kernel without 64 bit time support. Once ENOSYS is obtained, only 32-bit clock_gettime are used. The following snippet: clock_gettime (CLOCK_REALTIME, &(struct timespec) { 0 }); clock_gettime (CLOCK_MONOTONIC, &(struct timespec) { 0 }); clock_gettime (CLOCK_BOOTTIME, &(struct timespec) { 0 }); clock_gettime (20, &(struct timespec) { 0 }); On a kernel without 64 bit time support and with vDSO support results on the following syscalls: syscall_0x193(0, 0xff87ba30, [...]) = -1 ENOSYS (Function not implemented) clock_gettime(CLOCK_BOOTTIME, {tv_sec=927082, tv_nsec=474382032}) = 0 clock_gettime(0x14 /* CLOCK_??? */, 0xff87b9f8) = -1 EINVAL (Invalid argument) While on a kernel without vDSO support: syscall_0x193(0, 0xbec95550, 0xb6ed2000, 0x1, 0xbec95550, 0) = -1 (errno 38) clock_gettime(CLOCK_REALTIME, {tv_sec=1576615930, tv_nsec=638250162}) = 0 clock_gettime(CLOCK_MONOTONIC, {tv_sec=1665478, tv_nsec=638779620}) = 0 clock_gettime(CLOCK_BOOTTIME, {tv_sec=1675418, tv_nsec=292932704}) = 0 clock_gettime(0x14 /* CLOCK_??? */, 0xbec95530) = -1 EINVAL (Invalid argument) Checked on i686-linux-gnu on 4.15 kernel and on a 5.3 kernel. Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>		2020-01-03 11:22:07 -03:00
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linux	linux: Optimize fallback 32-bit clock_gettime	2020-01-03 11:22:07 -03:00