diff options
| author | Michael Kerrisk <mtk.manpages@gmail.com> | 2013-09-05 12:55:47 +0200 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2013-09-05 12:55:47 +0200 |
| commit | 78638aae3035d85ca027c003f480ff5d7921fac0 (patch) | |
| tree | 4bdb79686c028567215120b1c9b5dd00df675478 | |
| parent | 783d6cb45442ca83d1be338b22ce22e7181d0b9d (diff) | |
clock_getres.2: Note circumstances in which "SMP" note applies.
Reported-by: Rodrigo Campos <rodrigo@sdfg.com.ar>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
| -rw-r--r-- | man2/clock_getres.2 | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/man2/clock_getres.2 b/man2/clock_getres.2 index 9e872f62..ae7af1b6 100644 --- a/man2/clock_getres.2 +++ b/man2/clock_getres.2 @@ -221,12 +221,13 @@ are available. (See also .BR sysconf (3).) .SH NOTES -.SS Note for SMP systems -The +.SS Historical note for SMP systems +Before Linux added kernel support for .B CLOCK_PROCESS_CPUTIME_ID and -.B CLOCK_THREAD_CPUTIME_ID -clocks are realized on many platforms using timers from the CPUs +.BR CLOCK_THREAD_CPUTIME_ID , +glibc implemented these clocks on many platforms using timer +registers from the CPUs (TSC on i386, AR.ITC on Itanium). These registers may differ between CPUs and as a consequence these clocks may return @@ -252,6 +253,15 @@ Glibc contains no provisions to deal with these offsets (unlike the Linux Kernel). Typically these offsets are small and therefore the effects may be negligible in most cases. + +Since glibc 2.4, +the wrapper functions for the system calls described in this page avoid +the abovementioned problems by employing the kernel implementation of +.B CLOCK_PROCESS_CPUTIME_ID +and +.BR CLOCK_THREAD_CPUTIME_ID , +on systems that provide such an implementation +(i.e., Linux 2.6.12 and later). .SH BUGS According to POSIX.1-2001, a process with "appropriate privileges" may set the .B CLOCK_PROCESS_CPUTIME_ID |