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Top Forums Programming C Sleep function hangs @ __kernel_vsyscall () Post 302531454 by achenle on Thursday 16th of June 2011 08:36:29 PM
Old 06-16-2011
Quote:
Originally Posted by jim mcnamara
Are you blocking SIGALRM? sleep usually works by setting a timer, then sending a SIGALRM signal to the calling process.
That's normally no longer true.

And in this case, its pretty likely that sleep() has been implemented with a version of nanoslee().

It would be nice to see what the actual source code is, though.

If you look, it appears as if the file "sleep.c" calls __nanosleep_nocancel() directly. That could be something in the way libc actually links in nanosleep(), but maybe not? And if what's supposed to be an internal call is being used incorrectly, maybe the sleep time is a very large 64-bit integer - and the call does have "nocancel" appended to it....
 

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sleep(1)							   User Commands							  sleep(1)

NAME
sleep - suspend execution for an interval SYNOPSIS
/usr/bin/sleep /usr/bin/sleep time ksh93 sleep time DESCRIPTION
/usr/bin/sleep sleep suspends execution for at least the integral number of seconds specified by time. ksh93 sleep suspends execution for at least the time in seconds specified by time or until a SIGALRM signal is received. OPERANDS
/usr/bin/sleep The following operands are supported for /usr/bin/sleep: time time in seconds can be specified as a non-negative decimal integer number. ksh93 The following operands are supported: time Specify time in seconds as a floating point number. The actual granularity depends on the underlying system, normally around 1 mil- lisecond. EXAMPLES
Example 1 Suspending Command Execution The following example executes a command after a certain amount of time: example% (sleep 105; command)& Example 2 Executing a Command Every So Often The following example executes a command every so often: example% while true do command sleep 37 done ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables that affect the execution of sleep: LANG, LC_ALL, LC_CTYPE, LC_MES- SAGES, and NLSPATH. EXIT STATUS
The following exit values are returned: 0 The execution was successfully suspended for at least time seconds, or a SIGALRM signal was received (see NOTES). >0 An error has occurred. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: /usr/bin/sleep +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ |Interface Stability |Committed | +-----------------------------+-----------------------------+ |Standard |See standards(5). | +-----------------------------+-----------------------------+ ksh93 +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ |Interface Stability |Uncommitted | +-----------------------------+-----------------------------+ SEE ALSO
ksh93(1), wait(1), alarm(2), sleep(3C), wait(3UCB), attributes(5), environ(5), standards(5) NOTES
If the sleep utility receives a SIGALRM signal, one of the following actions is taken: o Terminate normally with a zero exit status. o Effectively ignore the signal. The sleep utility takes the standard action for all other signals. SunOS 5.11 20 Nov 2007 sleep(1)
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