From 45deb508575711c47d78d19e326a9a26e43e63e0 Mon Sep 17 00:00:00 2001
From: Apple <opensource@apple.com>
Date: Fri, 1 May 2020 18:18:24 +0000
Subject: [PATCH] libpthread-416.100.3.tar.gz

---
 src/pthread_asm.s   | 13 +++++++------
 src/pthread_mutex.c |  9 ++++++++-
 tests/stack.c       |  6 +++++-
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/src/pthread_asm.s b/src/pthread_asm.s
index 244957a..2a02f09 100644
--- a/src/pthread_asm.s
+++ b/src/pthread_asm.s
@@ -279,7 +279,7 @@ _thread_start:
 	.globl _thread_chkstk_darwin
 _thread_chkstk_darwin:
 	.globl ____chkstk_darwin
-____chkstk_darwin: // %w9 == alloca size
+____chkstk_darwin: // %w9/x9 == alloca size
 	stp     x10, x11, [sp, #-16]
 
 	// validate that the frame pointer is on our stack (no alt stack)
@@ -288,6 +288,7 @@ ____chkstk_darwin: // %w9 == alloca size
 
 	// (%sp - pthread_self()->stackaddr) > 0 ?
 #if defined(__ARM64_ARCH_8_32__)
+	ubfx    x9, x9, #0, #32
 	ldur    w11, [x10, _PTHREAD_STRUCT_DIRECT_STACKADDR_OFFSET]
 #else
 	ldur    x11, [x10, _PTHREAD_STRUCT_DIRECT_STACKADDR_OFFSET]
@@ -305,8 +306,8 @@ ____chkstk_darwin: // %w9 == alloca size
 	cmp     x10, x11
 	b.ls    Lprobe
 
-	// %sp - (uintptr_t)%w9 < pthread_self()->stackbottom ?
-	subs    x10, x10, w9, uxtw
+	// %sp - (uintptr_t)%x9 < pthread_self()->stackbottom ?
+	subs    x10, x10, x9
 	b.lo    Lcrash
 	cmp     x10, x11
 	b.lo    Lcrash
@@ -326,13 +327,13 @@ Lcrash:
 
 Lprobe:
 	mov     x10, sp
-	cmp     w9, #0x1000
+	cmp     x9, #0x1000
 	b.lo    Lend
 Lloop:
 	sub     x10, x10, #0x1000
 	ldr     x11, [x10]
-	sub     w9, w9, #0x1000
-	cmp     w9, #0x1000
+	sub     x9, x9, #0x1000
+	cmp     x9, #0x1000
 	b.hi    Lloop
 Lend:
 	sub     x10, x10, x9
diff --git a/src/pthread_mutex.c b/src/pthread_mutex.c
index e1e5c2e..ad86eeb 100644
--- a/src/pthread_mutex.c
+++ b/src/pthread_mutex.c
@@ -1444,7 +1444,7 @@ _pthread_mutex_firstfit_lock(pthread_mutex_t *omutex, bool trylock)
 	mutex_seq oldseq, newseq;
 	mutex_seq_load(seqaddr, &oldseq);
 
-	if (os_unlikely(oldseq.lgenval & PTH_RWL_EBIT)) {
+	if (os_unlikely(!trylock && (oldseq.lgenval & PTH_RWL_EBIT))) {
 		return _pthread_mutex_firstfit_lock_slow(mutex, trylock);
 	}
 
@@ -1454,9 +1454,16 @@ _pthread_mutex_firstfit_lock(pthread_mutex_t *omutex, bool trylock)
 		gotlock = is_rwl_ebit_clear(oldseq.lgenval);
 
 		if (trylock && !gotlock) {
+#if __LP64__
+			// The sequence load is atomic, so we can bail here without writing
+			// it and avoid some unnecessary coherence traffic - rdar://57259033
+			os_atomic_thread_fence(acquire);
+			return EBUSY;
+#else
 			// A trylock on a held lock will fail immediately. But since
 			// we did not load the sequence words atomically, perform a
 			// no-op CAS64 to ensure that nobody has unlocked concurrently.
+#endif
 		} else if (os_likely(gotlock)) {
 			// In first-fit, getting the lock simply adds the E-bit
 			newseq.lgenval |= PTH_RWL_EBIT;
diff --git a/tests/stack.c b/tests/stack.c
index f9458ad..f7d7fd0 100644
--- a/tests/stack.c
+++ b/tests/stack.c
@@ -50,7 +50,11 @@ T_DECL(chkstk, "chkstk",
 	};
 	T_ASSERT_POSIX_SUCCESS(sigaction(SIGSEGV, &sa, NULL), "sigaction");
 
-	call_chkstk(1 << 24);
+#if __LP64__
+	call_chkstk(1ul << 32);
+#else
+	call_chkstk(1ul << 24);
+#endif
 	T_FAIL("should have crashed");
 #endif
 }
-- 
2.47.2