| rmlock.9 (227588) | rmlock.9 (233648) |
|---|---|
| 1.\" Copyright (c) 2007 Stephan Uphoff <ups@FreeBSD.org> 2.\" Copyright (c) 2006 Gleb Smirnoff <glebius@FreeBSD.org> 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright --- 9 unchanged lines hidden (view full) --- 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" | 1.\" Copyright (c) 2007 Stephan Uphoff <ups@FreeBSD.org> 2.\" Copyright (c) 2006 Gleb Smirnoff <glebius@FreeBSD.org> 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright --- 9 unchanged lines hidden (view full) --- 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" |
| 26.\" $FreeBSD: head/share/man/man9/rmlock.9 227588 2011-11-16 21:51:17Z pjd $ | 26.\" $FreeBSD: head/share/man/man9/rmlock.9 233648 2012-03-29 05:02:12Z eadler $ |
| 27.\" 28.\" Based on rwlock.9 man page 29.Dd November 16, 2011 30.Dt RMLOCK 9 31.Os 32.Sh NAME 33.Nm rmlock , 34.Nm rm_init , --- 40 unchanged lines hidden (view full) --- 75A thread with exclusive access is known as a 76.Em writer 77since it can modify protected data. 78.Pp 79Read mostly locks are designed to be efficient for locks almost exclusively 80used as reader locks and as such should be used for protecting data that 81rarely changes. 82Acquiring an exclusive lock after the lock had been locked for shared access | 27.\" 28.\" Based on rwlock.9 man page 29.Dd November 16, 2011 30.Dt RMLOCK 9 31.Os 32.Sh NAME 33.Nm rmlock , 34.Nm rm_init , --- 40 unchanged lines hidden (view full) --- 75A thread with exclusive access is known as a 76.Em writer 77since it can modify protected data. 78.Pp 79Read mostly locks are designed to be efficient for locks almost exclusively 80used as reader locks and as such should be used for protecting data that 81rarely changes. 82Acquiring an exclusive lock after the lock had been locked for shared access |
| 83is an expensive operation. | 83is an expensive operation. |
| 84.Pp 85Although reader/writer locks look very similar to 86.Xr sx 9 87locks, their usage pattern is different. 88Reader/writer locks can be treated as mutexes (see 89.Xr mutex 9 ) 90with shared/exclusive semantics unless initialized with 91.Dv RM_SLEEPABLE . --- 99 unchanged lines hidden (view full) --- 191The 192.Fn rm_wlock 193function cannot be called recursively. 194.It Fn rm_runlock "struct rmlock *rm" "struct rm_priotracker* tracker" 195This function releases a shared lock previously acquired by 196.Fn rm_rlock . 197The 198.Fa tracker | 84.Pp 85Although reader/writer locks look very similar to 86.Xr sx 9 87locks, their usage pattern is different. 88Reader/writer locks can be treated as mutexes (see 89.Xr mutex 9 ) 90with shared/exclusive semantics unless initialized with 91.Dv RM_SLEEPABLE . --- 99 unchanged lines hidden (view full) --- 191The 192.Fn rm_wlock 193function cannot be called recursively. 194.It Fn rm_runlock "struct rmlock *rm" "struct rm_priotracker* tracker" 195This function releases a shared lock previously acquired by 196.Fn rm_rlock . 197The 198.Fa tracker |
| 199argument must match the 200.Fa tracker 201argument used for acquiring the shared lock | 199argument must match the 200.Fa tracker 201argument used for acquiring the shared lock |
| 202.It Fn rm_wunlock "struct rmlock *rm" 203This function releases an exclusive lock previously acquired by 204.Fn rm_wlock . 205.It Fn rm_destroy "struct rmlock *rm" 206This functions destroys a lock previously initialized with 207.Fn rm_init . 208The 209.Fa rm --- 33 unchanged lines hidden (view full) --- 243can fail transiently even when there is no writer, while another reader 244updates the state on the local CPU. 245.Pp 246The 247.Nm 248implementation uses a single per CPU list shared by all 249rmlocks in the system. 250If rmlocks become popular, hashing to multiple per CPU queues may | 202.It Fn rm_wunlock "struct rmlock *rm" 203This function releases an exclusive lock previously acquired by 204.Fn rm_wlock . 205.It Fn rm_destroy "struct rmlock *rm" 206This functions destroys a lock previously initialized with 207.Fn rm_init . 208The 209.Fa rm --- 33 unchanged lines hidden (view full) --- 243can fail transiently even when there is no writer, while another reader 244updates the state on the local CPU. 245.Pp 246The 247.Nm 248implementation uses a single per CPU list shared by all 249rmlocks in the system. 250If rmlocks become popular, hashing to multiple per CPU queues may |
| 251be needed to speed up the writer lock process. | 251be needed to speed up the writer lock process. |
| 252.Pp 253The 254.Nm 255can currently not be used as a lock argument for condition variable 256wait functions. | 252.Pp 253The 254.Nm 255can currently not be used as a lock argument for condition variable 256wait functions. |