05-01-2009
does sending a signal cause task switching
Hi all,
i am porting a system, that used to manipulate memory across processes using an interrupt handler - which means that upon return from the interrupt handler the memory change would be finished. I am trying to simulate this using signals on Linux 2.6.2x.
What i would like to know is wether sending a signal (ex. kill( pid , SIGUSR1 ) ) from a process will cause the kernel to perform taskswitching and put the calling process in queue, allowing the signal handler to run if it is ready?
A simplified scenario:
We have a shared memory area attached to both processes "share".
Process1:
...
share->variable = 0;
kill( Process2_pid , SIGUSR1 )
printf("share->variable= %d\n",share->variable);
...
Process2:
SIGUSR1_handler()
{
share->variable = 1;
}
It seems that the printf allways prints a "1" . Which would mean that taskswitching occurs, and that the handler in process2 has finished when process1 returns from kill().
But is this something one can rely on Running Linux 2.6.2x ?
Regards
Paul
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KILL(1) User Commands KILL(1)
NAME
kill - send a signal to a process
SYNOPSIS
kill [options] <pid> [...]
DESCRIPTION
The default signal for kill is TERM. Use -l or -L to list available signals. Particularly useful signals include HUP, INT, KILL, STOP,
CONT, and 0. Alternate signals may be specified in three ways: -9, -SIGKILL or -KILL. Negative PID values may be used to choose whole
process groups; see the PGID column in ps command output. A PID of -1 is special; it indicates all processes except the kill process
itself and init.
OPTIONS
<pid> [...]
Send signal to every <pid> listed.
-<signal>
-s <signal>
--signal <signal>
Specify the signal to be sent. The signal can be specified by using name or number. The behavior of signals is explained in sig-
nal(7) manual page.
-l, --list [signal]
List signal names. This option has optional argument, which will convert signal number to signal name, or other way round.
-L, --table
List signal names in a nice table.
NOTES Your shell (command line interpreter) may have a built-in kill command. You may need to run the command described here as /bin/kill
to solve the conflict.
EXAMPLES
kill -9 -1
Kill all processes you can kill.
kill -l 11
Translate number 11 into a signal name.
kill -L
List the available signal choices in a nice table.
kill 123 543 2341 3453
Send the default signal, SIGTERM, to all those processes.
SEE ALSO
kill(2), killall(1), nice(1), pkill(1), renice(1), signal(7), skill(1)
STANDARDS
This command meets appropriate standards. The -L flag is Linux-specific.
AUTHOR
Albert Cahalan <albert@users.sf.net> wrote kill in 1999 to replace a bsdutils one that was not standards compliant. The util-linux one
might also work correctly.
REPORTING BUGS
Please send bug reports to <procps@freelists.org>
procps-ng October 2011 KILL(1)