| dllockinit.3 (108087) | dllockinit.3 (131504) |
|---|---|
| 1.\" 2.\" Copyright (c) 1999, 2000 John D. Polstra 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.\" 2.\" Copyright (c) 1999, 2000 John D. Polstra 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/lib/libc/gen/dllockinit.3 108087 2002-12-19 09:40:28Z ru $ | 26.\" $FreeBSD: head/lib/libc/gen/dllockinit.3 131504 2004-07-02 23:52:20Z ru $ |
| 27.\" 28.Dd July 5, 2000 29.Os 30.Dt DLLOCKINIT 3 31.Sh NAME 32.Nm dllockinit 33.Nd register thread locking methods with the dynamic linker 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In dlfcn.h 38.Ft void 39.Fn dllockinit "void *context" "void *(*lock_create)(void *context)" "void (*rlock_acquire)(void *lock)" "void (*wlock_acquire)(void *lock)" "void (*lock_release)(void *lock)" "void (*lock_destroy)(void *lock)" "void (*context_destroy)(void *context)" 40.Sh DESCRIPTION 41.Bf Sy 42Due to enhancements in the dynamic linker, this interface is no longer | 27.\" 28.Dd July 5, 2000 29.Os 30.Dt DLLOCKINIT 3 31.Sh NAME 32.Nm dllockinit 33.Nd register thread locking methods with the dynamic linker 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In dlfcn.h 38.Ft void 39.Fn dllockinit "void *context" "void *(*lock_create)(void *context)" "void (*rlock_acquire)(void *lock)" "void (*wlock_acquire)(void *lock)" "void (*lock_release)(void *lock)" "void (*lock_destroy)(void *lock)" "void (*context_destroy)(void *context)" 40.Sh DESCRIPTION 41.Bf Sy 42Due to enhancements in the dynamic linker, this interface is no longer |
| 43needed. It is deprecated and will be removed from future releases. | 43needed. 44It is deprecated and will be removed from future releases. |
| 44In current releases it still exists, but only as a stub which does nothing. 45.Ef 46.Pp 47Threads packages can call 48.Fn dllockinit 49at initialization time to register locking functions for the dynamic | 45In current releases it still exists, but only as a stub which does nothing. 46.Ef 47.Pp 48Threads packages can call 49.Fn dllockinit 50at initialization time to register locking functions for the dynamic |
| 50linker to use. This enables the dynamic linker to prevent multiple | 51linker to use. 52This enables the dynamic linker to prevent multiple |
| 51threads from entering its critical sections simultaneously. 52.Pp 53The 54.Fa context | 53threads from entering its critical sections simultaneously. 54.Pp 55The 56.Fa context |
| 55argument specifies an opaque context for creating locks. The | 57argument specifies an opaque context for creating locks. 58The |
| 56dynamic linker will pass it to the 57.Fa lock_create | 59dynamic linker will pass it to the 60.Fa lock_create |
| 58function when creating the locks it needs. When the dynamic linker | 61function when creating the locks it needs. 62When the dynamic linker |
| 59is permanently finished using the locking functions (e.g., if the 60program makes a subsequent call to 61.Fn dllockinit 62to register new locking functions) it will call 63.Fa context_destroy 64to destroy the context. 65.Pp 66The 67.Fa lock_create | 63is permanently finished using the locking functions (e.g., if the 64program makes a subsequent call to 65.Fn dllockinit 66to register new locking functions) it will call 67.Fa context_destroy 68to destroy the context. 69.Pp 70The 71.Fa lock_create |
| 68argument specifies a function for creating a read/write lock. It | 72argument specifies a function for creating a read/write lock. 73It |
| 69must return a pointer to the new lock. 70.Pp 71The 72.Fa rlock_acquire 73and 74.Fa wlock_acquire 75arguments specify functions which lock a lock for reading or | 74must return a pointer to the new lock. 75.Pp 76The 77.Fa rlock_acquire 78and 79.Fa wlock_acquire 80arguments specify functions which lock a lock for reading or |
| 76writing, respectively. The | 81writing, respectively. 82The |
| 77.Fa lock_release | 83.Fa lock_release |
| 78argument specifies a function which unlocks a lock. Each of these | 84argument specifies a function which unlocks a lock. 85Each of these |
| 79functions is passed a pointer to the lock. 80.Pp 81The 82.Fa lock_destroy | 86functions is passed a pointer to the lock. 87.Pp 88The 89.Fa lock_destroy |
| 83argument specifies a function to destroy a lock. It may be | 90argument specifies a function to destroy a lock. 91It may be |
| 84.Dv NULL | 92.Dv NULL |
| 85if locks do not need to be destroyed. The | 93if locks do not need to be destroyed. 94The |
| 86.Fa context_destroy | 95.Fa context_destroy |
| 87argument specifies a function to destroy the context. It may be | 96argument specifies a function to destroy the context. 97It may be |
| 88.Dv NULL 89if the context does not need to be destroyed. 90.Pp 91Until 92.Fn dllockinit 93is called, the dynamic linker protects its critical sections using 94a default locking mechanism which works by blocking the 95.Dv SIGVTALRM , 96.Dv SIGPROF , 97and 98.Dv SIGALRM | 98.Dv NULL 99if the context does not need to be destroyed. 100.Pp 101Until 102.Fn dllockinit 103is called, the dynamic linker protects its critical sections using 104a default locking mechanism which works by blocking the 105.Dv SIGVTALRM , 106.Dv SIGPROF , 107and 108.Dv SIGALRM |
| 99signals. This is sufficient for many application level threads | 109signals. 110This is sufficient for many application level threads |
| 100packages, which typically use one of these signals to implement | 111packages, which typically use one of these signals to implement |
| 101preemption. An application which has registered its own locking | 112preemption. 113An application which has registered its own locking |
| 102methods with 103.Fn dllockinit 104can restore the default locking by calling 105.Fn dllockinit 106with all arguments 107.Dv NULL . 108.Sh SEE ALSO 109.Xr rtld 1 , 110.Xr signal 3 111.Sh HISTORY 112The 113.Fn dllockinit 114function first appeared in 115.Fx 4.0 . | 114methods with 115.Fn dllockinit 116can restore the default locking by calling 117.Fn dllockinit 118with all arguments 119.Dv NULL . 120.Sh SEE ALSO 121.Xr rtld 1 , 122.Xr signal 3 123.Sh HISTORY 124The 125.Fn dllockinit 126function first appeared in 127.Fx 4.0 . |