glibc/pthread-cond-wait-revert.patch

http://sourceware.org/ml/libc-alpha/2012-01/msg00002.html

The following patch:
Has been reported as causing numerous problems in Fedora & Debian.  I
don't think anyone has done any serious analysis of the issue, but the
patch has been pulled from both distributions because of the
instability it's introduced.

https://bugzilla.redhat.com/show_bug.cgi?id=769421
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=651899


commit c5a0802a682dba23f92d47f0f99775aebfbe2539
Author: Andreas Schwab <schwab@redhat.com>
Date:   Mon Nov 28 13:38:19 2011 +0100

    Handle EAGAIN from FUTEX_WAIT_REQUEUE_PI

2011-11-28  Andreas Schwab  <schwab@redhat.com>

	* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S: Handle
	EAGAIN from FUTEX_WAIT_REQUEUE_PI.
	* sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S: Likewise.

 
Index: glibc-2.15.90/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S
===================================================================
--- glibc-2.15.90.orig/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S
+++ glibc-2.15.90/nptl/sysdeps/unix/sysv/linux/i386/i486/pthread_cond_wait.S
@@ -136,7 +136,6 @@ __pthread_cond_wait:
 	cmpl	$PI_BIT, %eax
 	jne	18f
 
-90:
 	movl	$(FUTEX_WAIT_REQUEUE_PI|FUTEX_PRIVATE_FLAG), %ecx
 	movl	%ebp, %edx
 	xorl	%esi, %esi
@@ -150,9 +149,6 @@ __pthread_cond_wait:
 	sete	16(%esp)
 	je	19f
 
-	cmpl	$-EAGAIN, %eax
-	je	91f
-
 	/* Normal and PI futexes dont mix. Use normal futex functions only
 	   if the kernel does not support the PI futex functions.  */
 	cmpl	$-ENOSYS, %eax
@@ -397,78 +393,6 @@ __pthread_cond_wait:
 #endif
 	call	__lll_unlock_wake
 	jmp	11b
-
-91:
-.LcleanupSTART2:
-	/* FUTEX_WAIT_REQUEUE_PI returned EAGAIN.  We need to
-	   call it again.  */
-
-	/* Get internal lock.  */
-	movl	$1, %edx
-	xorl	%eax, %eax
-	LOCK
-#if cond_lock == 0
-	cmpxchgl %edx, (%ebx)
-#else
-	cmpxchgl %edx, cond_lock(%ebx)
-#endif
-	jz	92f
-
-#if cond_lock == 0
-	movl	%ebx, %edx
-#else
-	leal	cond_lock(%ebx), %edx
-#endif
-#if (LLL_SHARED-LLL_PRIVATE) > 255
-	xorl	%ecx, %ecx
-#endif
-	cmpl	$-1, dep_mutex(%ebx)
-	setne	%cl
-	subl	$1, %ecx
-	andl	$(LLL_SHARED-LLL_PRIVATE), %ecx
-#if LLL_PRIVATE != 0
-	addl	$LLL_PRIVATE, %ecx
-#endif
-	call	__lll_lock_wait
-
-92:
-	/* Increment the cond_futex value again, so it can be used as a new
-	   expected value. */
-	addl	$1, cond_futex(%ebx)
-	movl	cond_futex(%ebx), %ebp
-
-	/* Unlock.  */
-	LOCK
-#if cond_lock == 0
-	subl	$1, (%ebx)
-#else
-	subl	$1, cond_lock(%ebx)
-#endif
-	je	93f
-#if cond_lock == 0
-	movl	%ebx, %eax
-#else
-	leal	cond_lock(%ebx), %eax
-#endif
-#if (LLL_SHARED-LLL_PRIVATE) > 255
-	xorl	%ecx, %ecx
-#endif
-	cmpl	$-1, dep_mutex(%ebx)
-	setne	%cl
-	subl	$1, %ecx
-	andl	$(LLL_SHARED-LLL_PRIVATE), %ecx
-#if LLL_PRIVATE != 0
-	addl	$LLL_PRIVATE, %ecx
-#endif
-	call	__lll_unlock_wake
-
-93:
-	/* Set the rest of SYS_futex args for FUTEX_WAIT_REQUEUE_PI. */
-	xorl	%ecx, %ecx
-	movl	dep_mutex(%ebx), %edi
-	jmp	90b
-.LcleanupEND2:
-
 	.size	__pthread_cond_wait, .-__pthread_cond_wait
 versioned_symbol (libpthread, __pthread_cond_wait, pthread_cond_wait,
 		  GLIBC_2_3_2)
@@ -641,10 +565,6 @@ __condvar_w_cleanup:
 	.long	.LcleanupEND-.Lsub_cond_futex
 	.long	__condvar_w_cleanup-.LSTARTCODE
 	.uleb128  0
-	.long	.LcleanupSTART2-.LSTARTCODE
-	.long	.LcleanupEND2-.LcleanupSTART2
-	.long	__condvar_w_cleanup-.LSTARTCODE
-	.uleb128  0
 	.long	.LcallUR-.LSTARTCODE
 	.long	.LENDCODE-.LcallUR
 	.long	0
Index: glibc-2.15.90/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S
===================================================================
--- glibc-2.15.90.orig/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S
+++ glibc-2.15.90/nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S
@@ -136,14 +136,11 @@ __pthread_cond_wait:
 	cmpl	$PI_BIT, %eax
 	jne	61f
 
-90:
 	movl	$(FUTEX_WAIT_REQUEUE_PI|FUTEX_PRIVATE_FLAG), %esi
 	movl	$SYS_futex, %eax
 	syscall
 
 	movl	$1, %r8d
-	cmpq	$-EAGAIN, %rax
-	je	91f
 #ifdef __ASSUME_REQUEUE_PI
 	jmp	62f
 #else
@@ -331,69 +328,6 @@ __pthread_cond_wait:
 13:	movq	%r10, %rax
 	jmp	14b
 
-91:
-.LcleanupSTART2:
-	/* FUTEX_WAIT_REQUEUE_PI returned EAGAIN.  We need to
-	   call it again.  */
-	movq	8(%rsp), %rdi
-
-	/* Get internal lock.  */
-	movl	$1, %esi
-	xorl	%eax, %eax
-	LOCK
-#if cond_lock == 0
-	cmpxchgl %esi, (%rdi)
-#else
-	cmpxchgl %esi, cond_lock(%rdi)
-#endif
-	jz	92f
-
-#if cond_lock != 0
-	addq	$cond_lock, %rdi
-#endif
-	LP_OP(cmp) $-1, dep_mutex-cond_lock(%rdi)
-	movl	$LLL_PRIVATE, %eax
-	movl	$LLL_SHARED, %esi
-	cmovne	%eax, %esi
-	callq	__lll_lock_wait
-#if cond_lock != 0
-	subq	$cond_lock, %rdi
-#endif
-92:
-	/* Increment the cond_futex value again, so it can be used as a new
-	   expected value. */
-	incl	cond_futex(%rdi)
-	movl	cond_futex(%rdi), %edx
-
-	/* Release internal lock.  */
-	LOCK
-#if cond_lock == 0
-	decl	(%rdi)
-#else
-	decl	cond_lock(%rdi)
-#endif
-	jz	93f
-
-#if cond_lock != 0
-	addq	$cond_lock, %rdi
-#endif
-	LP_OP(cmp) $-1, dep_mutex-cond_lock(%rdi)
-	movl	$LLL_PRIVATE, %eax
-	movl	$LLL_SHARED, %esi
-	cmovne	%eax, %esi
-	/* The call preserves %rdx.  */
-	callq	__lll_unlock_wake
-#if cond_lock != 0
-	subq	$cond_lock, %rdi
-#endif
-93:
-	/* Set the rest of SYS_futex args for FUTEX_WAIT_REQUEUE_PI. */
-	xorq	%r10, %r10
-	mov	dep_mutex(%rdi), %R8_LP
-	leaq	cond_futex(%rdi), %rdi
-	jmp	90b
-.LcleanupEND2:
-
 	.size	__pthread_cond_wait, .-__pthread_cond_wait
 versioned_symbol (libpthread, __pthread_cond_wait, pthread_cond_wait,
 		  GLIBC_2_3_2)
@@ -546,15 +480,11 @@ __condvar_cleanup1:
 	.uleb128 .LcleanupSTART-.LSTARTCODE
 	.uleb128 .LcleanupEND-.LcleanupSTART
 	.uleb128 __condvar_cleanup1-.LSTARTCODE
-	.uleb128 0
-	.uleb128 .LcleanupSTART2-.LSTARTCODE
-	.uleb128 .LcleanupEND2-.LcleanupSTART2
-	.uleb128 __condvar_cleanup1-.LSTARTCODE
-	.uleb128 0
+	.uleb128  0
 	.uleb128 .LcallUR-.LSTARTCODE
 	.uleb128 .LENDCODE-.LcallUR
 	.uleb128 0
-	.uleb128 0
+	.uleb128  0
 .Lcstend: