diff options
-rw-r--r-- | libjava/ChangeLog | 5 | ||||
-rw-r--r-- | libjava/sysdep/pa/locks.h | 62 |
2 files changed, 52 insertions, 15 deletions
diff --git a/libjava/ChangeLog b/libjava/ChangeLog index 09821fe..cff2e26 100644 --- a/libjava/ChangeLog +++ b/libjava/ChangeLog @@ -1,3 +1,8 @@ +2005-12-28 John David Anglin <dave.anglin@nrc-cnrc.gc.ca> + + * sysdep/pa/locks.h (compare_and_swap): Add ldcw semaphore to make + operation atomic. + 2005-12-22 Andrew Haley <aph@redhat.com> PR java/25535 diff --git a/libjava/sysdep/pa/locks.h b/libjava/sysdep/pa/locks.h index 3f24afc..4edc2d7 100644 --- a/libjava/sysdep/pa/locks.h +++ b/libjava/sysdep/pa/locks.h @@ -1,6 +1,6 @@ -// locks.h - Thread synchronization primitives. PARISC implementation. +// locks.h - Thread synchronization primitives. PA-RISC implementation. -/* Copyright (C) 2002 Free Software Foundation +/* Copyright (C) 2002, 2005 Free Software Foundation This file is part of libgcj. @@ -11,30 +11,62 @@ details. */ #ifndef __SYSDEP_LOCKS_H__ #define __SYSDEP_LOCKS_H__ -typedef size_t obj_addr_t; /* Integer type big enough for object */ - /* address. */ +// Integer type big enough for object address. +typedef size_t obj_addr_t; -// Atomically replace *addr by new_val if it was initially equal to old. -// Return true if the comparison succeeded. +template<int _Inst> + struct _pa_jv_cas_lock + { + static volatile int _S_pa_jv_cas_lock; + }; + +template<int _Inst> +volatile int +_pa_jv_cas_lock<_Inst>::_S_pa_jv_cas_lock __attribute__ ((aligned (16))) = 1; + +// Because of the lack of weak support when using the hpux som +// linker, we explicitly instantiate the atomicity lock. +template volatile int _pa_jv_cas_lock<0>::_S_pa_jv_cas_lock; + +// Atomically replace *addr by new_val if it was initially equal to old_val. +// Return true if the comparison is successful. // Assumed to have acquire semantics, i.e. later memory operations // cannot execute before the compare_and_swap finishes. +// The following implementation is atomic but it can deadlock +// (e.g., if a thread dies holding the lock). inline static bool +__attribute__ ((__unused__)) compare_and_swap(volatile obj_addr_t *addr, - obj_addr_t old, + obj_addr_t old_val, obj_addr_t new_val) { - /* FIXME: not atomic */ - obj_addr_t prev; + bool result; + int tmp; + volatile int& lock = _pa_jv_cas_lock<0>::_S_pa_jv_cas_lock; - if ((prev = *addr) == old) - { - *addr = new_val; - return true; - } + __asm__ __volatile__ ("ldcw 0(%1),%0\n\t" + "cmpib,<>,n 0,%0,.+20\n\t" + "ldw 0(%1),%0\n\t" + "cmpib,= 0,%0,.-4\n\t" + "nop\n\t" + "b,n .-20" + : "=&r" (tmp) + : "r" (&lock) + : "memory"); + + if (*addr != old_val) + result = false; else { - return false; + *addr = new_val; + result = true; } + + /* Reset lock with PA 2.0 "ordered" store. */ + __asm__ __volatile__ ("stw,ma %1,0(%0)" + : : "r" (&lock), "r" (tmp) : "memory"); + + return result; } // Set *addr to new_val with release semantics, i.e. making sure |