Date: Fri, 18 May 2018 04:13:58 +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: r333781 - head/share/man/man9 Message-ID: <201805180413.w4I4DwNZ086096@repo.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: mmacy Date: Fri May 18 04:13:58 2018 New Revision: 333781 URL: https://svnweb.freebsd.org/changeset/base/333781 Log: epoch(9): fix error in example and update API reference Submitted by: hps Approved by: sbruno Modified: head/share/man/man9/epoch.9 Modified: head/share/man/man9/epoch.9 ============================================================================== --- head/share/man/man9/epoch.9 Fri May 18 04:13:58 2018 (r333780) +++ head/share/man/man9/epoch.9 Fri May 18 04:13:58 2018 (r333781) @@ -45,14 +45,20 @@ .In sys/proc.h .In sys/epoch.h .Ft epoch_t -.Fn epoch_alloc "void" +.Fn epoch_alloc "int flags" .Ft void .Fn epoch_enter "epoch_t epoch" .Ft void +.Fn epoch_enter_critical "epoch_t epoch" +.Ft void .Fn epoch_exit "epoch_t epoch" .Ft void +.Fn epoch_exit_critical "epoch_t epoch" +.Ft void .Fn epoch_wait "epoch_t epoch" .Ft void +.Fn epoch_wait_critical "epoch_t epoch" +.Ft void .Fn epoch_call "epoch_t epoch" "epoch_context_t ctx" "void (*callback) (epoch_context_t)" .Ft int .Fn in_epoch "void" @@ -66,14 +72,24 @@ Epochs are allocated with .Fn epoch_alloc and freed with .Fn epoch_free . +The flags passed to epoch_alloc determine whether preemption is +allowed during a section (the default) or not, as specified by +EPOCH_CRITICAL. Threads indicate the start of an epoch critical section by calling .Fn epoch_enter . The end of a critical section is indicated by calling .Fn epoch_exit . +The _critical variants can be used around code in which it is safe +to have preemption disable. A thread can wait until a grace period has elapsed since any threads have entered the epoch by calling .Fn epoch_wait . +The use of a EPOCH_CRITICAL epoch type allows one to use +.Fn epoch_wait_critical +which is guaranteed to have much shorter completion times since +we know that none of the threads in an epoch section will be preempted +before completing its section. If the thread can't sleep or is otherwise in a performance sensitive path it can ensure that a grace period has elapsed by calling .Fn epoch_call @@ -106,8 +122,12 @@ Async free example: Thread 1: .Bd -literal +int +in_pcbladdr(struct inpcb *inp, struct in_addr *faddr, struct in_laddr *laddr, + struct ucred *cred) { - epoch_enter(net_epoch); + /* ... */ + epoch_enter(net_epoch); CK_STAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) { sa = ifa->ifa_addr; if (sa->sa_family != AF_INET) @@ -119,6 +139,7 @@ Thread 1: } } epoch_exit(net_epoch); + /* ... */ } .Ed Thread 2: @@ -131,12 +152,13 @@ ifa_free(struct ifaddr *ifa) epoch_call(net_epoch, &ifa->ifa_epoch_ctx, ifa_destroy); } +void +if_purgeaddrs(struct ifnet *ifp) { + /* .... */ IF_ADDR_WLOCK(ifp); CK_STAILQ_REMOVE(&ifp->if_addrhead, ifa, ifaddr, ifa_link); - /* mark as unlinked */ - ifa->ifa_addr->sa_family = AF_UNSPEC; IF_ADDR_WUNLOCK(ifp); ifa_free(ifa); }
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201805180413.w4I4DwNZ086096>