polyrabbit commented on a change in pull request #1031:
URL: https://github.com/apache/incubator-brpc/pull/1031#discussion_r820148410
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File path: src/bthread/rwlock.cpp
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@@ -0,0 +1,163 @@
+#include <pthread.h>
+#include <execinfo.h>
+#include <dlfcn.h> // dlsym
+#include <fcntl.h> // O_RDONLY
+#include "butil/atomicops.h"
+#include "bvar/bvar.h"
+#include "bvar/collector.h"
+#include "butil/macros.h" // BAIDU_CASSERT
+#include "butil/containers/flat_map.h"
+#include "butil/iobuf.h"
+#include "butil/fd_guard.h"
+#include "butil/files/file.h"
+#include "butil/files/file_path.h"
+#include "butil/file_util.h"
+#include "butil/unique_ptr.h"
+#include "butil/third_party/murmurhash3/murmurhash3.h"
+#include "butil/logging.h"
+#include "butil/object_pool.h"
+#include "bthread/butex.h" // butex_*
+#include "bthread/processor.h" // cpu_relax, barrier
+#include "bthread/bthread.h"
+#include "bthread/sys_futex.h"
+#include "bthread/log.h"
+
+
+namespace bthread {
+
+inline int rwlock_unrlock(bthread_rwlock_t* rwlock) {
+ butil::atomic<unsigned>* whole =
+ (butil::atomic<unsigned>*)rwlock->lock_flag;
+
+ while(1) {
+ unsigned r = whole->load();
+ if(r==0 || (r>>31) != 0) {
+ LOG(ERROR) << "wrong unrlock!";
+ return 0;
+ }
+ if(!(whole->compare_exchange_weak(r, r-1))) {
+ continue;
+ }
+ //wake up write waiter
+ bthread::butex_wake(whole);
+ return 0;
+ }
+
+}
+
+
+inline int rwlock_unwlock(bthread_rwlock_t* rwlock) {
+ butil::atomic<unsigned>* whole =
+ (butil::atomic<unsigned>*)rwlock->lock_flag;
+
+ while(1) {
+ unsigned r = whole->load();
+ if(r != (unsigned)(1<<31) ) {
+ LOG(ERROR) << "wrong unwlock!";
+ return 0;
+ }
+ if(!whole->compare_exchange_weak(r, 0)) {
+ continue;
+ }
+ //wake up write waiter first
+ bthread::butex_wake(whole);
+ butil::atomic<unsigned>* w_wait_count =
(butil::atomic<unsigned>*)rwlock->w_wait_count;
+ //try reduce wait_count for read waiters,and wake up read waiters
+ w_wait_count->fetch_sub(1);
+ bthread::butex_wake_all(w_wait_count);
+ return 0;
+ }
+
+}
+
+
+inline int rwlock_unlock(bthread_rwlock_t* rwlock) {
+ butil::atomic<unsigned>* whole =
+ (butil::atomic<unsigned>*)rwlock->lock_flag;
+ if ((whole->load(butil::memory_order_relaxed) >> 31) != 0) {
+ return rwlock_unwlock(rwlock);
+ } else {
+ return rwlock_unrlock(rwlock);
+ }
+}
+
+inline int rwlock_rlock(bthread_rwlock_t* rwlock) {
+ butil::atomic<unsigned>* whole =
+ (butil::atomic<unsigned>*)rwlock->lock_flag;
+
+ butil::atomic<unsigned>* w_wait_count =
(butil::atomic<unsigned>*)rwlock->w_wait_count;
+ while (1) {
+ unsigned w = w_wait_count->load();
+ if( w > 0) {
+ if(bthread::butex_wait(w_wait_count, w, NULL) < 0 &&
+ errno != EWOULDBLOCK && errno != EINTR) {
+ return errno;
+ }
+ continue;
+ }
+ //FIXME!! we don't consider read_wait_count overflow yet,2^31 should
be enough here
+ unsigned r = whole->load();
+ if((r >> 31) == 0) {
+ if(whole->compare_exchange_weak(r, r + 1)) {
+ return 0;
+ }
+ }
+ }
+
+}
+
+inline int rwlock_wlock(bthread_rwlock_t* rwlock) {
+ butil::atomic<unsigned>* w_wait_count =
(butil::atomic<unsigned>*)rwlock->w_wait_count;
+ butil::atomic<unsigned>* whole =
(butil::atomic<unsigned>*)rwlock->lock_flag;
+ //we don't consider w_wait_count overflow yet,2^32 should be enough here
+ w_wait_count->fetch_add(1);
+ while(1) {
+ unsigned r = whole->load();
+ if(r != 0) {
+ if(bthread::butex_wait(whole, r, NULL) < 0 &&
+ errno != EWOULDBLOCK && errno != EINTR) {
+ whole->fetch_sub(1);
Review comment:
这里需要减一的为啥是`whole`？我感觉应该是`w_wait_count`吧？
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