Introduce pthread_rwlock_try{rd,wr}lock

This also changes recursive mutexes to favor cpu over scheduler yield.

libc/calls/calls.mk

@@ -145,6 +145,8 @@ o/$(MODE)/libc/calls/tailcontext.o: libc/calls/tailcontext.S
 	@$(COMPILE) -AOBJECTIFY.S $(OBJECTIFY.S) $(OUTPUT_OPTION) -c $<
 o/$(MODE)/libc/calls/stackjump.o: libc/calls/stackjump.S
 	@$(COMPILE) -AOBJECTIFY.S $(OBJECTIFY.S) $(OUTPUT_OPTION) -c $<
+o/$(MODE)/libc/calls/sched_yield.o: libc/calls/sched_yield.S
+	@$(COMPILE) -AOBJECTIFY.S $(OBJECTIFY.S) $(OUTPUT_OPTION) -c $<
 
 LIBC_CALLS_LIBS = $(foreach x,$(LIBC_CALLS_ARTIFACTS),$($(x)))
 LIBC_CALLS_SRCS = $(foreach x,$(LIBC_CALLS_ARTIFACTS),$($(x)_SRCS))

libc/intrin/intrin.mk

@@ -119,8 +119,6 @@ o/$(MODE)/libc/intrin/ksockoptnames.o: libc/intrin/ksockoptnames.S
 	@$(COMPILE) -AOBJECTIFY.S $(OBJECTIFY.S) $(OUTPUT_OPTION) -c $<
 o/$(MODE)/libc/intrin/ktcpoptnames.o: libc/intrin/ktcpoptnames.S
 	@$(COMPILE) -AOBJECTIFY.S $(OBJECTIFY.S) $(OUTPUT_OPTION) -c $<
-o/$(MODE)/libc/intrin/sched_yield.o: libc/intrin/sched_yield.S
-	@$(COMPILE) -AOBJECTIFY.S $(OBJECTIFY.S) $(OUTPUT_OPTION) -c $<
 o/$(MODE)/libc/intrin/stackcall.o: libc/intrin/stackcall.S
 	@$(COMPILE) -AOBJECTIFY.S $(OBJECTIFY.S) $(OUTPUT_OPTION) -c $<
 

libc/intrin/pthread_mutex_lock.c

@@ -22,6 +22,7 @@
 #include "libc/intrin/atomic.h"
 #include "libc/intrin/strace.internal.h"
 #include "libc/intrin/weaken.h"
+#include "libc/nexgen32e/yield.h"
 #include "libc/runtime/internal.h"
 #include "libc/thread/thread.h"
 #include "libc/thread/tls.h"
@@ -64,7 +65,7 @@
  * @see pthread_spin_lock()
  * @vforksafe
  */
-int pthread_mutex_lock(pthread_mutex_t *mutex) {
+errno_t pthread_mutex_lock(pthread_mutex_t *mutex) {
   int t;
 
   LOCKTRACE("pthread_mutex_lock(%t)", mutex);
@@ -82,7 +83,7 @@ int pthread_mutex_lock(pthread_mutex_t *mutex) {
 
   if (mutex->_type == PTHREAD_MUTEX_NORMAL) {
     while (atomic_exchange_explicit(&mutex->_lock, 1, memory_order_acquire)) {
-      pthread_yield();
+      spin_yield();
     }
     return 0;
   }
@@ -102,7 +103,7 @@ int pthread_mutex_lock(pthread_mutex_t *mutex) {
   }
 
   while (atomic_exchange_explicit(&mutex->_lock, 1, memory_order_acquire)) {
-    pthread_yield();
+    spin_yield();
   }
 
   mutex->_depth = 0;

libc/intrin/pthread_mutex_trylock.c

@@ -1,7 +1,7 @@
 /*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
 │vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
 ╞══════════════════════════════════════════════════════════════════════════════╡
-│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│ Copyright 2023 Justine Alexandra Roberts Tunney                              │
 │                                                                              │
 │ Permission to use, copy, modify, and/or distribute this software for         │
 │ any purpose with or without fee is hereby granted, provided that the         │
@@ -19,27 +19,29 @@
 #include "libc/calls/calls.h"
 #include "libc/errno.h"
 #include "libc/intrin/atomic.h"
-#include "libc/intrin/kprintf.h"
 #include "libc/intrin/weaken.h"
+#include "libc/runtime/internal.h"
 #include "libc/thread/thread.h"
-#include "libc/thread/tls.h"
 #include "third_party/nsync/mu.h"
 
 /**
- * Locks mutex if it isn't locked already.
+ * Attempts acquiring lock.
  *
  * Unlike pthread_mutex_lock() this function won't block and instead
  * returns an error immediately if the lock couldn't be acquired.
  *
- * @return 0 on success, or errno on error
- * @raise EBUSY if lock is already held
- * @raise ENOTRECOVERABLE if `mutex` is corrupted
+ * @return 0 if lock was acquired, otherwise an errno
+ * @raise EAGAIN if maximum number of recursive locks is held
+ * @raise EBUSY if lock is currently held in read or write mode
+ * @raise EINVAL if `mutex` doesn't refer to an initialized lock
+ * @raise EDEADLK if `mutex` is `PTHREAD_MUTEX_ERRORCHECK` and the
+ *     current thread already holds this mutex
  */
 errno_t pthread_mutex_trylock(pthread_mutex_t *mutex) {
   int t;
 
-  if (__tls_enabled &&                               //
-      mutex->_type == PTHREAD_MUTEX_NORMAL &&        //
+  // delegate to *NSYNC if possible
+  if (mutex->_type == PTHREAD_MUTEX_NORMAL &&
       mutex->_pshared == PTHREAD_PROCESS_PRIVATE &&  //
       _weaken(nsync_mu_trylock)) {
     if (_weaken(nsync_mu_trylock)((nsync_mu *)mutex)) {
@@ -49,6 +51,7 @@ errno_t pthread_mutex_trylock(pthread_mutex_t *mutex) {
     }
   }
 
+  // handle normal mutexes
   if (mutex->_type == PTHREAD_MUTEX_NORMAL) {
     if (!atomic_exchange_explicit(&mutex->_lock, 1, memory_order_acquire)) {
       return 0;
@@ -57,6 +60,7 @@ errno_t pthread_mutex_trylock(pthread_mutex_t *mutex) {
     }
   }
 
+  // handle recursive and error check mutexes
   t = gettid();
   if (mutex->_owner == t) {
     if (mutex->_type != PTHREAD_MUTEX_ERRORCHECK) {
@@ -67,15 +71,17 @@ errno_t pthread_mutex_trylock(pthread_mutex_t *mutex) {
         return EAGAIN;
       }
     } else {
-      return EBUSY;
+      return EDEADLK;
     }
   }
 
-  if (!atomic_exchange_explicit(&mutex->_lock, 1, memory_order_acquire)) {
-    mutex->_depth = 0;
-    mutex->_owner = t;
-    return 0;
-  } else {
+  if (atomic_exchange_explicit(&mutex->_lock, 1, memory_order_acquire)) {
     return EBUSY;
   }
+
+  mutex->_depth = 0;
+  mutex->_owner = t;
+  mutex->_pid = __pid;
+
+  return 0;
 }

libc/intrin/pthread_mutex_unlock.c

@@ -34,7 +34,7 @@
  * @raises EPERM if in error check mode and not owned by caller
  * @vforksafe
  */
-int pthread_mutex_unlock(pthread_mutex_t *mutex) {
+errno_t pthread_mutex_unlock(pthread_mutex_t *mutex) {
   int t;
 
   LOCKTRACE("pthread_mutex_unlock(%t)", mutex);

libc/intrin/pthread_next.c

@@ -19,6 +19,7 @@
 #include "libc/assert.h"
 #include "libc/dce.h"
 #include "libc/intrin/atomic.h"
+#include "libc/nexgen32e/yield.h"
 #include "libc/thread/posixthread.internal.h"
 
 intptr_t _pthread_syshand(struct PosixThread *pt) {
@@ -27,6 +28,6 @@ intptr_t _pthread_syshand(struct PosixThread *pt) {
   for (;;) {
     syshand = atomic_load_explicit(&pt->tib->tib_syshand, memory_order_acquire);
     if (syshand) return syshand;
-    pthread_yield();
+    spin_yield();
   }
 }

libc/intrin/pthread_tid.c

@@ -17,12 +17,13 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/intrin/atomic.h"
+#include "libc/nexgen32e/yield.h"
 #include "libc/thread/posixthread.internal.h"
 
 int _pthread_tid(struct PosixThread *pt) {
   int tid = 0;
   while (pt && !(tid = atomic_load_explicit(&pt->ptid, memory_order_acquire))) {
-    pthread_yield();
+    spin_yield();
   }
   return tid;
 }

libc/thread/pthread_create.c

@@ -57,6 +57,7 @@
 
 __static_yoink("nsync_mu_lock");
 __static_yoink("nsync_mu_unlock");
+__static_yoink("nsync_mu_trylock");
 __static_yoink("nsync_mu_rlock");
 __static_yoink("nsync_mu_runlock");
 __static_yoink("_pthread_atfork");

libc/thread/pthread_rwlock_tryrdlock.c

@@ -0,0 +1,37 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2023 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/errno.h"
+#include "libc/thread/thread.h"
+#include "third_party/nsync/mu.h"
+
+/**
+ * Attempts acquiring read lock on read-write lock.
+ *
+ * @return 0 if lock was acquired, otherwise an errno
+ * @raise EBUSY if lock is currently held in write mode
+ * @raise EAGAIN if maximum number of read locks are held
+ * @raise EINVAL if `rwlock` doesn't refer to an initialized r/w lock
+ */
+errno_t pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock) {
+  if (nsync_mu_rtrylock((nsync_mu *)rwlock)) {
+    return 0;
+  } else {
+    return EBUSY;
+  }
+}

libc/thread/pthread_rwlock_trywrlock.c

@@ -0,0 +1,37 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2023 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/errno.h"
+#include "libc/thread/thread.h"
+#include "third_party/nsync/mu.h"
+
+/**
+ * Attempts acquiring write lock on read-write lock.
+ *
+ * @return 0 if lock was acquired, otherwise an errno
+ * @raise EBUSY if lock is currently held in read or write mode
+ * @raise EINVAL if `rwlock` doesn't refer to an initialized r/w lock
+ */
+errno_t pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock) {
+  if (nsync_mu_trylock((nsync_mu *)rwlock)) {
+    rwlock->_iswrite = 1;
+    return 0;
+  } else {
+    return EBUSY;
+  }
+}

test/libc/intrin/pthread_mutex_lock_test.c

@@ -43,6 +43,8 @@
 #define THREADS    8
 #define ITERATIONS 512
 
+#define MAX_RECURSIVE_LOCKS 64
+
 int count;
 atomic_int started;
 atomic_int finished;
@@ -79,11 +81,18 @@ TEST(pthread_mutex_lock, recursive) {
   ASSERT_EQ(0, pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE));
   ASSERT_EQ(0, pthread_mutex_init(&lock, &attr));
   ASSERT_EQ(0, pthread_mutexattr_destroy(&attr));
-  ASSERT_EQ(0, pthread_mutex_lock(&lock));
-  ASSERT_EQ(0, pthread_mutex_lock(&lock));
-  ASSERT_EQ(0, pthread_mutex_trylock(&lock));
-  ASSERT_EQ(0, pthread_mutex_unlock(&lock));
-  ASSERT_EQ(0, pthread_mutex_unlock(&lock));
+  for (int i = 0; i < MAX_RECURSIVE_LOCKS; ++i) {
+    if (i & 1) {
+      ASSERT_EQ(0, pthread_mutex_lock(&lock));
+    } else {
+      ASSERT_EQ(0, pthread_mutex_trylock(&lock));
+    }
+  }
+  ASSERT_EQ(EAGAIN, pthread_mutex_lock(&lock));
+  ASSERT_EQ(EAGAIN, pthread_mutex_trylock(&lock));
+  for (int i = 0; i < MAX_RECURSIVE_LOCKS; ++i) {
+    ASSERT_EQ(0, pthread_mutex_unlock(&lock));
+  }
   ASSERT_EQ(0, pthread_mutex_lock(&lock));
   ASSERT_EQ(0, pthread_mutex_unlock(&lock));
   ASSERT_EQ(0, pthread_mutex_unlock(&lock));
@@ -99,7 +108,7 @@ TEST(pthread_mutex_lock, errorcheck) {
   ASSERT_EQ(0, pthread_mutexattr_destroy(&attr));
   ASSERT_EQ(0, pthread_mutex_lock(&lock));
   ASSERT_EQ(EDEADLK, pthread_mutex_lock(&lock));
-  ASSERT_EQ(EBUSY, pthread_mutex_trylock(&lock));
+  ASSERT_EQ(EDEADLK, pthread_mutex_trylock(&lock));
   ASSERT_EQ(0, pthread_mutex_unlock(&lock));
   ASSERT_EQ(0, pthread_mutex_destroy(&lock));
 }