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Diffstat (limited to 'libthreads/alpha/lock.S')
| -rw-r--r-- | libthreads/alpha/lock.S | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/libthreads/alpha/lock.S b/libthreads/alpha/lock.S new file mode 100644 index 00000000..657ac1f8 --- /dev/null +++ b/libthreads/alpha/lock.S @@ -0,0 +1,84 @@ +/* + * Mach Operating System + * Copyright (c) 1992 Carnegie Mellon University + * All Rights Reserved. + * + * Permission to use, copy, modify and distribute this software and its + * documentation is hereby granted, provided that both the copyright + * notice and this permission notice appear in all copies of the + * software, derivative works or modified versions, and any portions + * thereof, and that both notices appear in supporting documentation. + * + * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" + * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR + * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. + * + * Carnegie Mellon requests users of this software to return to + * + * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU + * School of Computer Science + * Carnegie Mellon University + * Pittsburgh PA 15213-3890 + * + * any improvements or extensions that they make and grant Carnegie Mellon + * the rights to redistribute these changes. + */ +/* + * HISTORY + * $Log: lock.s,v $ + * Revision 2.3 93/03/09 10:59:04 danner + * Lost in previous merge: + * Added memory barriers where needed. + * Locks are longs now. + * [93/01/15 af] + * + * Revision 2.2 93/01/14 18:04:31 danner + * Mumble, "try_lock" really means "try_hard_once". + * That is, try hard until you either get it or lose it. + * [92/12/24 af] + * Created a while back. + * [92/12/10 af] + * + */ + +#include <mach/alpha/asm.h> + +/* + The C interface for this function is + + boolean_t + spin_try_lock_sw(m) + long * m; + + The function has a slightly different semantics than TAS: it will + return a boolean value that indicates whether the lock was acquired + or not. If not, we'll presume that the user will retry after some + appropriate delay. + */ + .text + .align 4 + .set noreorder + +LEAF(spin_try_lock,1) + mb + ldq_l t0,0(a0) + or zero,2,v0 /* build lock value */ + bne t0,nope /* already set, forget it */ + stq_c v0,0(a0) /* see if we still had the lock */ + beq v0,yipe /* if we just took an interrupt.. */ + RET /* if v0 != 0 then we got it */ +nope: + mov zero,v0 /* failed to acquire lock */ + RET +yipe: br zero,spin_try_lock /* I love branch predictions.. */ + + END(spin_try_lock) + +LEAF(spin_unlock,1) + mb /* but this might be needed.. */ + stq zero,0(a0) /* no need for interlocks (sec 10.5.2) */ + mb /* but this might be needed.. */ + RET + + END(spin_unlock) + |