Date: Sat, 24 Jul 2021 20:18:57 -0500 From: Matthew Grooms <mgrooms@shrew.net> To: freebsd-arm@freebsd.org Subject: aarch64 and kqueue timer events Message-ID: <03ff40c7-b755-8421-713c-90aa4d8535fe@shrew.net>
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Hi all,
I'm seeing some strange behavior with kqueue timers on my aarch64 host.
Here is a simple test program that I've compiled on both amd64 and
aarch64. It just sets up a simple kqueue timer with a loop that waits
for the event to fire every 3 seconds ...
#include <err.h>
#include <time.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/event.h>
int main( int argc, char *argv[] )
{
int kq = kqueue();
if( kq < 0 )
err( 1, "failed to obtain kqueue handle" );
struct kevent ke;
EV_SET( &ke, 1, EVFILT_TIMER, EV_ADD | EV_ENABLE, 0, 3000, 0 );
if( kevent( kq, &ke, 1, NULL, 0, NULL ) < 0 )
err( 1, "failed to add kevent timer filter" );
printf( "started at %i\n", (int)time(NULL) );
while( true )
{
int r = kevent( kq, NULL, 0, &ke, 1, NULL );
if( r < 0 )
err( 1, "failed to read kevent list" );
printf( "timer fired %i times at %i\n", r, (int)time(NULL) );
}
return 0;
}
When I compile and run the code on an amd64 host, everything works as
expected. The event timer expires once every 3 seconds ...
mgrooms@amd64:~/devel$ cc test.cpp -o test && ./test
started at 1627175311
timer fired 1 times at 1627175314
timer fired 1 times at 1627175317
timer fired 1 times at 1627175320
However, when I compile and run the same code on an aarch64 host ( rpi4b
), something very different happens. The event timer expires after 3
seconds the first time. But each subsequent expiration is for exactly
twice the defined interval, 6 seconds ...
mgrooms@aarch64:~/devel$ cc test.cpp -o test && ./test
started at 1625789207
timer fired 1 times at 1625789210
timer fired 1 times at 1625789216
timer fired 1 times at 1625789222
Any idea what's going on here? Seems like a bug in somewhere on the arm
side.
Thanks in advance,
-Matthew
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