On Jul 10, 2013, at 11:09 AM, John Baldwin <j...@freebsd.org> wrote:
> On Wednesday, July 10, 2013 2:05:43 pm John Baldwin wrote: >> On Wednesday, July 10, 2013 1:42:20 pm Marcel Moolenaar wrote: >>> Author: marcel >>> Date: Wed Jul 10 17:42:20 2013 >>> New Revision: 253161 >>> URL: http://svnweb.freebsd.org/changeset/base/253161 >>> >>> Log: >>> Protect against broken hardware. In this particular case, protect against >>> H/W not de-asserting the interrupt at all. On x86, and because of the >>> following conditions, this results in a hard hang with interrupts disabled: >>> 1. The uart(4) driver uses a spin lock to protect against concurrent >>> access to the H/W. Spin locks disable and restore interrupts. >>> 2. Restoring the interrupt on x86 always writes the flags register. Even >>> if we're restoring the interrupt from disabled to disabled. >>> 3. The x86 CPU has a short window in which interrupts are enabled when the >>> flags register is written. >> >> Do you have proof of this? No. I only have proof of a hard hang during auto configuration that cannot be fixed in any other way than not to setup the interrupt at all. -- Marcel Moolenaar mar...@xcllnt.net _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
