From nobody Sun Jul 25 01:18:57 2021 X-Original-To: freebsd-arm@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id BD65412A6754 for ; Sun, 25 Jul 2021 01:19:02 +0000 (UTC) (envelope-from mgrooms@shrew.net) Received: from mx2.shrew.net (mx2.shrew.net [38.97.5.132]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4GXQF168KFz3KBt for ; Sun, 25 Jul 2021 01:19:01 +0000 (UTC) (envelope-from mgrooms@shrew.net) Received: from mail.shrew.net (mail.shrew.prv [10.24.10.20]) by mx2.shrew.net (8.15.2/8.15.2) with ESMTP id 16P1Is3t056186 for ; Sat, 24 Jul 2021 20:18:54 -0500 (CDT) (envelope-from mgrooms@shrew.net) Received: from [10.22.200.30] (unknown [136.49.68.36]) by mail.shrew.net (Postfix) with ESMTPSA id 90C8119B153 for ; Sat, 24 Jul 2021 20:18:49 -0500 (CDT) To: freebsd-arm@freebsd.org From: Matthew Grooms Subject: aarch64 and kqueue timer events Message-ID: <03ff40c7-b755-8421-713c-90aa4d8535fe@shrew.net> Date: Sat, 24 Jul 2021 20:18:57 -0500 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 List-Id: Porting FreeBSD to ARM processors List-Archive: https://lists.freebsd.org/archives/freebsd-arm List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-arm@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx2.shrew.net [10.24.10.11]); Sat, 24 Jul 2021 20:18:54 -0500 (CDT) X-Rspamd-Queue-Id: 4GXQF168KFz3KBt X-Spamd-Bar: / Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=pass (mx1.freebsd.org: domain of mgrooms@shrew.net designates 38.97.5.132 as permitted sender) smtp.mailfrom=mgrooms@shrew.net X-Spamd-Result: default: False [-0.30 / 15.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; R_SPF_ALLOW(-0.20)[+mx]; MIME_GOOD(-0.10)[text/plain]; TO_DN_NONE(0.00)[]; PREVIOUSLY_DELIVERED(0.00)[freebsd-arm@freebsd.org]; RCPT_COUNT_ONE(0.00)[1]; RCVD_COUNT_THREE(0.00)[3]; DMARC_NA(0.00)[shrew.net]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:174, ipnet:38.0.0.0/8, country:US]; RCVD_TLS_LAST(0.00)[]; MAILMAN_DEST(0.00)[freebsd-arm]; RECEIVED_SPAMHAUS_PBL(0.00)[136.49.68.36:received] X-ThisMailContainsUnwantedMimeParts: N 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 #include #include #include #include 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