Date: Wed, 4 Jul 2018 03:44:36 +0000 (UTC) From: Matt Macy <mmacy@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r335929 - head/share/man/man9 Message-ID: <201807040344.w643iacq007523@repo.freebsd.org>
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Author: mmacy Date: Wed Jul 4 03:44:36 2018 New Revision: 335929 URL: https://svnweb.freebsd.org/changeset/base/335929 Log: epoch(9): update man page for r335924 Modified: head/share/man/man9/epoch.9 Modified: head/share/man/man9/epoch.9 ============================================================================== --- head/share/man/man9/epoch.9 Wed Jul 4 03:36:46 2018 (r335928) +++ head/share/man/man9/epoch.9 Wed Jul 4 03:44:36 2018 (r335929) @@ -49,11 +49,11 @@ .Ft void .Fn epoch_enter "epoch_t epoch" .Ft void -.Fn epoch_enter_preempt "epoch_t epoch" +.Fn epoch_enter_preempt "epoch_t epoch" "epoch_tracker_t et" .Ft void .Fn epoch_exit "epoch_t epoch" .Ft void -.Fn epoch_exit_preempt "epoch_t epoch" +.Fn epoch_exit_preempt "epoch_t epoch" "epoch_tracker_t et" .Ft void .Fn epoch_wait "epoch_t epoch" .Ft void @@ -104,12 +104,16 @@ INVARIANTS can assert that a thread is in an epoch by .Fn in_epoch . .Pp The epoch API currently does not support sleeping in epoch_preempt sections. -A caller cannot do epoch_enter recursively on different preemptible epochs. A caller should never call .Fn epoch_wait -in the middle of an epoch section as this will lead to a deadlock. +in the middle of an epoch section for the same epoch as this will lead to a deadlock. .Pp -Note that epochs are not a straight replacement for read locks. +Be default mutexes cannot be held across +.Fn epoch_wait_preempt . +To permit this the epoch must be allocated with +.Fn EPOCH_LOCKED . +When doing this one must be cautious of creating a situation where a deadlock is +possible. Note that epochs are not a straight replacement for read locks. Callers must use safe list and tailq traversal routines in an epoch (see ck_queue). When modifying a list referenced from an epoch section safe removal routines must be used and the caller can no longer modify a list entry
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