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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2019-12-16 13:50:57 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2020-01-03 11:22:07 -0300
commit92b963699aae2da1e25f47edc7a0408bf3aee4d2 (patch)
treeddd0d6395031f782246254f4ec643f9e68dbe46f /misc/mntent.h
parent0dc1a378b135ec46fcc451d96c4a3a64c08e2ace (diff)
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linux: Optimize fallback 32-bit clock_getres
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_getres (CLOCK_REALTIME, &(struct timespec) { 0 });
  clock_getres (CLOCK_MONOTONIC, &(struct timespec) { 0 });
  clock_getres (CLOCK_BOOTTIME, &(struct timespec) { 0 });
  clock_getres (20, &(struct timespec) { 0 });

On a kernel without 64 bit time support issues the syscalls:

  syscall_0x196(0, 0xffb83330, [...]) = -1 ENOSYS (Function not implemented)
  clock_getres(CLOCK_REALTIME, {tv_sec=0, tv_nsec=1}) = 0
  clock_getres(CLOCK_MONOTONIC, {tv_sec=0, tv_nsec=1}) = 0
  clock_getres(CLOCK_BOOTTIME, {tv_sec=0, tv_nsec=1}) = 0

Checked on i686-linux-gnu on 4.15 kernel.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Diffstat (limited to 'misc/mntent.h')
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