Date: Thu, 17 May 2018 04:27:08 +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: r333703 - head/sys/vm Message-ID: <201805170427.w4H4R8lv058775@repo.freebsd.org>
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Author: markj Date: Thu May 17 04:27:08 2018 New Revision: 333703 URL: https://svnweb.freebsd.org/changeset/base/333703 Log: Fix a race in vm_page_pagequeue_lockptr(). The value of m->queue must be cached after comparing it with PQ_NONE, since it may be concurrently changing. Reported by: glebius Reviewed by: jeff Differential Revision: https://reviews.freebsd.org/D15462 Modified: head/sys/vm/vm_page.c head/sys/vm/vm_page.h Modified: head/sys/vm/vm_page.c ============================================================================== --- head/sys/vm/vm_page.c Thu May 17 04:08:57 2018 (r333702) +++ head/sys/vm/vm_page.c Thu May 17 04:27:08 2018 (r333703) @@ -3088,10 +3088,11 @@ vm_page_pagequeue(vm_page_t m) static struct mtx * vm_page_pagequeue_lockptr(vm_page_t m) { + uint8_t queue; - if (m->queue == PQ_NONE) + if ((queue = m->queue) == PQ_NONE) return (NULL); - return (&vm_page_pagequeue(m)->pq_mutex); + return (&vm_pagequeue_domain(m)->vmd_pagequeues[queue].pq_mutex); } static inline void Modified: head/sys/vm/vm_page.h ============================================================================== --- head/sys/vm/vm_page.h Thu May 17 04:08:57 2018 (r333702) +++ head/sys/vm/vm_page.h Thu May 17 04:27:08 2018 (r333703) @@ -208,7 +208,7 @@ struct vm_page { uint16_t flags; /* page PG_* flags (P) */ uint8_t aflags; /* access is atomic */ uint8_t oflags; /* page VPO_* flags (O) */ - uint8_t queue; /* page queue index (Q) */ + volatile uint8_t queue; /* page queue index (Q) */ int8_t psind; /* pagesizes[] index (O) */ int8_t segind; /* vm_phys segment index (C) */ uint8_t order; /* index of the buddy queue (F) */
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