FreeBSD Errata Notice FreeBSD-EN-16:07.ipi
4 May, 2016 by firstname.lastname@example.org | freebsd
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-EN-16:07.ipi Errata Notice The FreeBSD Project Topic: Excessive latency in x86 IPI delivery Category: core Module: kernel Announced: 2016-05-04 Credits: Stanislav Sedov Affects: FreeBSD 10.2 and 10.3 Corrected: 2016-04-27 19:12:49 UTC (stable/10, 10.3-STABLE) 2016-05-04 15:25:47 UTC (releng/10.3, 10.3-RELEASE-p2) 2016-05-04 15:26:23 UTC (releng/10.2, 10.2-RELEASE-p16) For general information regarding FreeBSD Errata Notices and Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:https://security.freebsd.org/>. I. Background Each CPU in an x86 system contains an interrupt controller (local APIC) used to handle both external interrupts and inter-processor-interrupts (IPIs). II. Problem Description In xAPIC mode, the local APIC can only queue a single IPI at a time. If a previously queued IPI is still pending when a CPU attempts to send an IPI, it spins waiting for the previous IPI to complete. A change merged prior to 10.2-RELEASE altered this loop to check the state of the previous IPI once every 5 microseconds rather than constantly polling. III. Impact Checking the status of the previous IPI once every 5 microseconds could introduce 5 microsecond delays when sending IPIs. This could increase the latency of various scheduling operations reducing performance. IV. Workaround No workaround is available, but non-x86 systems are not affected. V. Solution Perform one of the following: 1) Upgrade your system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date. 2) To update your present system via a binary patch: Systems running a RELEASE version of FreeBSD on the i386 or amd64 platforms can be updated via the freebsd-update(8) utility: # freebsd-update fetch # freebsd-update install 3) To update your present system via a source code patch: The following patches have been verified to apply to the applicable FreeBSD release branches. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. # fetch https://security.FreeBSD.org/patches/EN-16:07/ipi.patch # fetch https://security.FreeBSD.org/patches/EN-16:07/ipi.patch.asc # gpg --verify ipi.patch.asc b) Apply the patch. Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile your kernel as described in <URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the system. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/10/ r298715 releng/10.2/ r299067 releng/10.3/ r299066 - ------------------------------------------------------------------------- To see which files were modified by a particular revision, run the following command, replacing NNNNNN with the revision number, on a machine with Subversion installed: # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base Or visit the following URL, replacing NNNNNN with the revision number: <URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN> VII. References The latest revision of this Errata Notice is available at https://security.FreeBSD.org/advisories/FreeBSD-EN-16:07.ipi.asc -----BEGIN PGP SIGNATURE----- iQIcBAEBCgAGBQJXKj3tAAoJEO1n7NZdz2rnbpMP/R/Xetx8IFIeP4Ez9IYvQPXM ylnDZiLn0AP2AW5Wn4Dxa6SyfrTGYOpjMSGFtxu6JqPczFYhYY0fYVkdwLqPu0DS 2Q9xGLJ0hedVa+aPbDyoS6Zafe2VElFjcpHm+y3qaaAhLoQNolMd+3bj0sezxzb/ mVJZq1vHzFKU84vmiBXb6zF6lcwJgEqbdeLyLT+y+p42Sne9/k6QIUPUQPZKciu/ gs3RH3/0NhNWyXRl8ISjU0uJB3SHFZTbbfRSoX/0pE0FGaaYue9UeOEAzsBi5O6x apF5euq6o6QSzH1MQaPj1hApreUY4TCS+/2ZSjKGTOZAOP9CkIjm/U89G5cw+dH4 Bs4jV4q0H1Pc3jHGP/Y0NyPDA7XrmNUjhw//8WodchqyeHkrSboy4K2Cd5AFS03e dM4fUz1ybTWYTAuHejKIN7yPKo1MsI7tX55fYXZtZ9iA+JhTYGBuJEoBVqlDiSte RcfYWjMY45srf5lPwTjauuHFjsfgvHwxuxyQyKPV+uysq9y7E2E6hypBYZ0SJNaz W6fEAyUFv8rM6qMxtANuuOVDDrRTYq/FId5AhMMheK9AONA3XcvL9otMqw5HMBtg kzOoQ0JJKUbDow8sy9mjtM0cOgoNvmfRlUuLXxV26swXEHZ4la0o16mNVEzo10Z9 mlbeuHCqBP25eT/TzQG4 =XoQ4 -----END PGP SIGNATURE----- _______________________________________________ email@example.com mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-announce To unsubscribe, send any mail to "firstname.lastname@example.org"