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am b61c5064: Merge "Work around atomic_load(const T*) issues."

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* commit 'b61c50647b85b3c33af8ca155e88ec098d9e8cb0':
  Work around atomic_load(const T*) issues.
This commit is contained in:
Hans Boehm
2014-08-20 20:48:45 +00:00
committed by Android Git Automerger
parent d61f102bf8 b61c50647b
commit c4b55c1221
1 changed files with 11 additions and 3 deletions
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14
libc/bionic/system_properties.cpp
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@@ -611,6 +611,14 @@ const prop_info *__system_property_find(const char *name)
return find_property(root_node(), name, strlen(name), NULL, 0, false); return find_property(root_node(), name, strlen(name), NULL, 0, false);
} }
// The C11 standard doesn't allow atomic loads from const fields,
// though C++11 does. Fudge it until standards get straightened out.
static inline uint_least32_t load_const_atomic(const atomic_uint_least32_t* s,
memory_order mo) {
atomic_uint_least32_t* non_const_s = const_cast<atomic_uint_least32_t*>(s);
return atomic_load_explicit(non_const_s, mo);
}
int __system_property_read(const prop_info *pi, char *name, char *value) int __system_property_read(const prop_info *pi, char *name, char *value)
{ {
if (__predict_false(compat_mode)) { if (__predict_false(compat_mode)) {
@@ -631,7 +639,7 @@ int __system_property_read(const prop_info *pi, char *name, char *value)
// would be any different, so this should be OK. // would be any different, so this should be OK.
atomic_thread_fence(memory_order_acquire); atomic_thread_fence(memory_order_acquire);
if (serial == if (serial ==
atomic_load_explicit(&(pi->serial), memory_order_relaxed)) { load_const_atomic(&(pi->serial), memory_order_relaxed)) {
if (name != 0) { if (name != 0) {
strcpy(name, pi->name); strcpy(name, pi->name);
} }
@@ -733,12 +741,12 @@ int __system_property_add(const char *name, unsigned int namelen,
// Wait for non-locked serial, and retrieve it with acquire semantics. // Wait for non-locked serial, and retrieve it with acquire semantics.
unsigned int __system_property_serial(const prop_info *pi) unsigned int __system_property_serial(const prop_info *pi)
{ {
uint32_t serial = atomic_load_explicit(&pi->serial, memory_order_acquire); uint32_t serial = load_const_atomic(&pi->serial, memory_order_acquire);
while (SERIAL_DIRTY(serial)) { while (SERIAL_DIRTY(serial)) {
__futex_wait(const_cast<volatile void *>( __futex_wait(const_cast<volatile void *>(
reinterpret_cast<const void *>(&pi->serial)), reinterpret_cast<const void *>(&pi->serial)),
serial, NULL); serial, NULL);
serial = atomic_load_explicit(&pi->serial, memory_order_acquire); serial = load_const_atomic(&pi->serial, memory_order_acquire);
} }
return serial; return serial;
} }