Date: Fri, 21 Feb 2020 09:00:22 +0000 From: bugzilla-noreply@freebsd.org To: usb@FreeBSD.org Subject: [Bug 226968] IRQ storm on cpu0 timer when holding down key on USB keyboard Message-ID: <bug-226968-19105-bC8eyPJHo2@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-226968-19105@https.bugs.freebsd.org/bugzilla/> References: <bug-226968-19105@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D226968 --- Comment #27 from commit-hook@freebsd.org --- A commit references this bug: Author: hselasky Date: Fri Feb 21 08:59:21 UTC 2020 New revision: 358215 URL: https://svnweb.freebsd.org/changeset/base/358215 Log: MFC r304735 and r331692: Fix key delay and repeat, part 2. Use sbintime_t timeouts with precision control to get very accurate timing. It costs little to always ask for about 1% accuracy, and the not so new event timer implementation usual delivers that, and when it can't it gets much closer than our previous coarse timeouts and buggy simple countdown. The 2 fastest atkbd repeat rates have periods 34 and 38 msec, and ukbd pretended to support rates in between these. This requires sub-microsecond precision and accuracy even to handle the 4 msec difference very well, but ukbd asked the timeout subsystem for timeouts of 25 msec and the buggy simple countdown of this gave a a wide range of precisions and accuracies depending on HZ and other timer configuration (sometimes better than 25 msec but usually more like 50 msec). We now ask for and usually get precision and accuracy of about 1% for each repeat and much better on average. The 1% accuracy is overkill. Rounding of 30 cps to 34 msec instead of 33 already gives an error of +2% instead of -1%, and ut AT keyboards on PS/2 interfaces have similar errors. A timeout is now scheduled for every keypress and release. This allows some simplifications that are not done. It allows removing the timeout scheduling for exiting polled mode where it was unsafe in ddb mode. This is done. Exiting polled mode had some problems with extra repeats. Now exiting polled mode lets an extra timeout fire and the state is fudged so that the timeout handler does very little. The sc->time_ms variable is unsigned to avoid overflow. Differences of it need to be signed. Signed comparisons were emulated by testing an emulated sign bits. This only works easily for '<' comparisonss, but we now need a '<=3D' comparison. Change the difference variable to signed and use a signed comparison. Using unsigned types here didn't prevent overflow bugs but just reduced them. Overflow occurs with n repeats at the silly repeat period of [U]INT_MAX / n. The old countdown had an off by 1 error, and the simplifications would simply count down 1 to 0 and not need to accumulate possibly-large repeat repeats. PR: 226968 Sponsored by: Mellanox Technologies Changes: _U stable/11/ stable/11/sys/dev/usb/input/ukbd.c --=20 You are receiving this mail because: You are the assignee for the bug.=
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