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Use rel semantics of cas instead of acq semantics with full barrier before it in _int_free

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The following patch fixes catomic_compare_and_exchange_*_rel definitions
(which were never used and weren't correct) and uses
catomic_compare_and_exchange_val_rel in _int_free.  Comparing to the
pre-2009-07-02 --enable-experimental-malloc state the generated code should
be identical on all arches other than ppc/ppc64 and on ppc/ppc64 should use
lwsync instead of isync barrier.
This commit is contained in:
Jakub Jelinek 2009-07-16 07:24:50 -07:00 committed by Ulrich Drepper
parent 55c4ce6885
commit bea0ac1d87
3 changed files with 35 additions and 13 deletions
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13
ChangeLog
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@ -1,3 +1,16 @@
2009-07-13 Jakub Jelinek <jakub@redhat.com>
* include/atomic.h (catomic_compare_and_exchange_val_rel): If arch
overrides atomic_compare_and_exchange_val_rel, define to
atomic_compare_and_exchange_val_rel by default, otherwise default
to catomic_compare_and_exchange_val_acq.
(catomic_compare_and_exchange_bool_rel): If arch overrides
atomic_compare_and_exchange_bool_rel, define to
atomic_compare_and_exchange_bool_rel by default.
* malloc/malloc.c (_int_free): Revert 2009-07-02 change.
Use catomic_compare_and_exchange_val_rel instead of
catomic_compare_and_exchange_val_acq.
2009-07-16 Ulrich Drepper <drepper@redhat.com>
* sysdeps/generic/ldsodefs.h: Add prototype for

28
include/atomic.h
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@ -107,14 +107,19 @@
#endif
#ifndef catomic_compare_and_exchange_val_rel
# ifndef atomic_compare_and_exchange_val_rel
# define atomic_compare_and_exchange_val_rel(mem, newval, oldval) \
atomic_compare_and_exchange_val_acq (mem, newval, oldval)
# define catomic_compare_and_exchange_val_rel(mem, newval, oldval) \
catomic_compare_and_exchange_val_acq (mem, newval, oldval)
# else
# define catomic_compare_and_exchange_val_rel(mem, newval, oldval) \
atomic_compare_and_exchange_val_rel (mem, newval, oldval)
# endif
#endif
#ifndef catomic_compare_and_exchange_val_rel
# define catomic_compare_and_exchange_val_rel(mem, newval, oldval) \
#ifndef atomic_compare_and_exchange_val_rel
# define atomic_compare_and_exchange_val_rel(mem, newval, oldval) \
atomic_compare_and_exchange_val_acq (mem, newval, oldval)
#endif
@ -155,15 +160,20 @@
#endif
#ifndef catomic_compare_and_exchange_bool_rel
# ifndef atomic_compare_and_exchange_bool_rel
# define atomic_compare_and_exchange_bool_rel(mem, newval, oldval) \
atomic_compare_and_exchange_bool_acq (mem, newval, oldval)
# define catomic_compare_and_exchange_bool_rel(mem, newval, oldval) \
catomic_compare_and_exchange_bool_acq (mem, newval, oldval)
# else
# define catomic_compare_and_exchange_bool_rel(mem, newval, oldval) \
atomic_compare_and_exchange_bool_rel (mem, newval, oldval)
# endif
#endif
#ifndef catomic_compare_and_exchange_bool_rel
# define catomic_compare_and_exchange_bool_rel(mem, newval, oldval) \
catomic_compare_and_exchange_bool_acq (mem, newval, oldval)
#ifndef atomic_compare_and_exchange_bool_rel
# define atomic_compare_and_exchange_bool_rel(mem, newval, oldval) \
atomic_compare_and_exchange_bool_acq (mem, newval, oldval)
#endif

3
malloc/malloc.c
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@ -4822,9 +4822,8 @@ _int_free(mstate av, mchunkptr p)
goto errout;
}
p->fd = fd = old;
atomic_full_barrier ();
}
while ((old = catomic_compare_and_exchange_val_acq (fb, p, fd)) != fd);
while ((old = catomic_compare_and_exchange_val_rel (fb, p, fd)) != fd);
#else
/* Another simple check: make sure the top of the bin is not the
record we are going to add (i.e., double free). */