Date: Tue, 18 Sep 2018 17:51:46 +0000 (UTC) From: Mark Johnston <markj@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r338755 - head/sys/vm Message-ID: <201809181751.w8IHpkUV062428@repo.freebsd.org>
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Author: markj Date: Tue Sep 18 17:51:45 2018 New Revision: 338755 URL: https://svnweb.freebsd.org/changeset/base/338755 Log: Only update the domain cursor once in keg_fetch_slab(). We drop the keg lock when we go to actually allocate the slab, allowing other threads to advance the cursor. This can cause us to exit the round-robin loop before having attempted allocations from all domains, resulting in a hang during a subsequent blocking allocation attempt from a depleted domain. Reported and tested by: Jan Bramkamp <crest@bultmann.eu> Reviewed by: alc, cem Approved by: re (gjb) Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D17209 Modified: head/sys/vm/uma_core.c Modified: head/sys/vm/uma_core.c ============================================================================== --- head/sys/vm/uma_core.c Tue Sep 18 16:57:04 2018 (r338754) +++ head/sys/vm/uma_core.c Tue Sep 18 17:51:45 2018 (r338755) @@ -2698,10 +2698,8 @@ again: LIST_INSERT_HEAD(&dom->ud_part_slab, slab, us_link); return (slab); } - if (rr) { - keg->uk_cursor = (keg->uk_cursor + 1) % vm_ndomains; - domain = keg->uk_cursor; - } + if (rr) + domain = (domain + 1) % vm_ndomains; } while (domain != start); /* Retry domain scan with blocking. */
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