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Noted that POSIX.1 leaves interactions with alarm(), sleep(), 

and usleep() unspecified.
Linux 2.6.16 removed the MAX_SEC_IN_JIFFIES ceiling on timer values.
Other minor changes.
This commit is contained in:
Michael Kerrisk 2008-06-23 10:28:23 +00:00
parent b81087ab66
commit 0102b0ab21
1 changed files with 18 additions and 4 deletions
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22
man2/getitimer.2
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@ -4,7 +4,7 @@
.\" Modified Tue Oct 22 00:22:35 EDT 1996 by Eric S. Raymond <esr@thyrsus.com>
.\" 2005-04-06 mtk, Matthias Lang <matthias@corelatus.se>
.\" Noted MAX_SEC_IN_JIFFIES ceiling
.TH GETITIMER 2 2006-04-27 "Linux" "Linux Programmer's Manual"
.TH GETITIMER 2 2008-04-24 "Linux" "Linux Programmer's Manual"
.SH NAME
getitimer, setitimer \- get or set value of an interval timer
.SH SYNOPSIS
@ -84,7 +84,7 @@ sets the indicated timer to the value in
.IR value .
If
.I ovalue
is non-zero, the old value of the timer is stored there.
is non-NULL, the old value of the timer is stored there.
.LP
Timers decrement from
.I it_value
@ -104,7 +104,8 @@ are significant in determining the duration of a timer.
.LP
Timers will never expire before the requested time,
but may expire some (short) time afterwards, which depends
on the system timer resolution and on the system load.
on the system timer resolution and on the system load; see
.BR time (7).
(But see BUGS below.)
Upon expiration, a signal will be generated and the timer reset.
If the timer expires while the process is active (always true for
@ -145,6 +146,16 @@ A child created via
does not inherit its parent's interval timers.
Interval timers are preserved across an
.BR execve (2).
POSIX.1 leaves the
interaction between
.BR setitimer()
and
.BR alarm (2),
.BR sleep (3),
and
.BR usleep (3)
unspecified.
.SH BUGS
The generation and delivery of a signal are distinct, and
only one instance of each of the signals listed above may be pending
@ -155,7 +166,7 @@ timer may expire before the signal from a previous expiration
has been delivered.
The second signal in such an event will be lost.
On Linux, timer values are represented in jiffies.
On Linux kernels before 2.6.16, timer values are represented in jiffies.
If a request is made set a timer with a value whose jiffies
representation exceeds
.B MAX_SEC_IN_JIFFIES
@ -166,6 +177,9 @@ On Linux/i386 (where, since Linux 2.6.13,
the default jiffy is 0.004 seconds),
this means that the ceiling value for a timer is
approximately 99.42 days.
Since Linux 2.6.16,
the kernel uses a different internal representation for times,
and this ceiling is removed.
On certain systems (including i386),
Linux kernels before version 2.6.12 have a bug which will produce