Ankita Garg wrote:
Hi,
There is a testcase called 'pthread_kill_latency' under the rt-test suite
on the the RT Wiki:
http://www.kernel.org/pub/linux/kernel/people/dvhart/realtime/tests/rt-test-0.3.tar.bz2
Description of the testcase:
The test measures the latency involved in sending a signal to a thread
using pthread_kill. Two threads are created, receiver thread (thread1)
and sender thread (thread2). Before sending the signal, it waits for
thread1 to initialize (thread1 waits by calling sigwait), notes the time and
send pthread_kill signal to thread1. thread1 notes the time it receives the
signal. The maximum and the minimum latency is reported. This is repeated
about 10000 times.
I'm looking at the source. The receiver thread runs with realtime
priority (it's created with create_fifo_thread), but the sender thread
(thread2) doesn't (create_other_thread). The sender does:
/* Record the time just before sending the signal */
begin = rt_gettime();
/**** The sender can get preempted by anything right here ! ****/
if ((ret = pthread_kill(PTHREADOF(target_thread), SIGNALNUMBER))) {
printf("pthread_kill returned %d\n", ret);
}
Can this explain it?
Michal
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