Date: Mon, 30 Jul 2018 11:41:52 +0000 (UTC) From: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= <royger@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r336897 - head/sys/dev/xen/grant_table Message-ID: <201807301141.w6UBfq4j093191@repo.freebsd.org>
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Author: royger Date: Mon Jul 30 11:41:51 2018 New Revision: 336897 URL: https://svnweb.freebsd.org/changeset/base/336897 Log: xen/grants: fix deadlocks in the free callbacks This fixes the panic caused by deadlocking when grant-table free callbacks are used. The cause of the recursion is: check_free_callbacks() is always called with the lock gnttab_list_lock held. In turn the callback function is also called with the lock held. Then when the client uses any of the grant reference methods which also attempt the lock the gnttab_list_lock mutex from within the free callback a deadlock happens. Fix this by making the gnttab_list_lock recursive. Submitted by: Pratyush Yadav <pratyush@freebsd.org> Differential Revision: https://reviews.freebsd.org/D16505 Modified: head/sys/dev/xen/grant_table/grant_table.c Modified: head/sys/dev/xen/grant_table/grant_table.c ============================================================================== --- head/sys/dev/xen/grant_table/grant_table.c Mon Jul 30 11:27:51 2018 (r336896) +++ head/sys/dev/xen/grant_table/grant_table.c Mon Jul 30 11:41:51 2018 (r336897) @@ -585,7 +585,7 @@ gnttab_expand(unsigned int req_entries) return (error); } -MTX_SYSINIT(gnttab, &gnttab_list_lock, "GNTTAB LOCK", MTX_DEF); +MTX_SYSINIT(gnttab, &gnttab_list_lock, "GNTTAB LOCK", MTX_DEF | MTX_RECURSE); /*------------------ Private Device Attachment Functions --------------------*/ /**
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