Re: aarch64 and kqueue timer events
- Reply: Christian Ullrich : "Re: aarch64 and kqueue timer events"
- In reply to: Matthew Grooms : "aarch64 and kqueue timer events"
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Date: Sun, 25 Jul 2021 01:21:55 UTC
On 7/24/2021 8:18 PM, Matthew Grooms wrote: > 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. Sorry. Forgot to mention the OS version. It's 13 stable on the aarch64 side ... FreeBSD generic 13.0-STABLE FreeBSD 13.0-STABLE #8 stable/13-n246015-ade8b810b02-dirty: Tue Jun 15 21:04:38 CDT 2021 -Matthew