path: root/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S

/* Copyright (C) 2002-2016 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <sysdep.h>
#include <shlib-compat.h>
#include <lowlevellock.h>
#include <lowlevelcond.h>
#include <tcb-offsets.h>
#include <pthread-pi-defines.h>
#include <pthread-errnos.h>
#include <stap-probe.h>

#include <kernel-features.h>


	.text

/* int pthread_cond_wait (pthread_cond_t *cond, pthread_mutex_t *mutex)  */
	.globl	__pthread_cond_wait
	.type	__pthread_cond_wait, @function
	.align	16
__pthread_cond_wait:
.LSTARTCODE:
	cfi_startproc
#ifdef SHARED
	cfi_personality(DW_EH_PE_pcrel | DW_EH_PE_sdata4 | DW_EH_PE_indirect,
			DW.ref.__gcc_personality_v0)
	cfi_lsda(DW_EH_PE_pcrel | DW_EH_PE_sdata4, .LexceptSTART)
#else
	cfi_personality(DW_EH_PE_udata4, __gcc_personality_v0)
	cfi_lsda(DW_EH_PE_udata4, .LexceptSTART)
#endif

#define FRAME_SIZE (32+8)
	leaq	-FRAME_SIZE(%rsp), %rsp
	cfi_adjust_cfa_offset(FRAME_SIZE)

	/* Stack frame:

	   rsp + 32
		    +--------------------------+
	   rsp + 24 | old wake_seq value       |
		    +--------------------------+
	   rsp + 16 | mutex pointer            |
		    +--------------------------+
	   rsp +  8 | condvar pointer          |
		    +--------------------------+
	   rsp +  4 | old broadcast_seq value  |
		    +--------------------------+
	   rsp +  0 | old cancellation mode    |
		    +--------------------------+
	*/

	LIBC_PROBE (cond_wait, 2, %rdi, %rsi)

	LP_OP(cmp) $-1, dep_mutex(%rdi)

	/* Prepare structure passed to cancellation handler.  */
	movq	%rdi, 8(%rsp)
	movq	%rsi, 16(%rsp)

	je	15f
	mov	%RSI_LP, dep_mutex(%rdi)

	/* Get internal lock.  */
15:	movl	$1, %esi
	xorl	%eax, %eax
	LOCK
#if cond_lock == 0
	cmpxchgl %esi, (%rdi)
#else
	cmpxchgl %esi, cond_lock(%rdi)
#endif
	jne	1f

	/* Unlock the mutex.  */
2:	movq	16(%rsp), %rdi
	xorl	%esi, %esi
	callq	__pthread_mutex_unlock_usercnt

	testl	%eax, %eax
	jne	12f

	movq	8(%rsp), %rdi
	incq	total_seq(%rdi)
	incl	cond_futex(%rdi)
	addl	$(1 << nwaiters_shift), cond_nwaiters(%rdi)

	/* Get and store current wakeup_seq value.  */
	movq	8(%rsp), %rdi
	movq	wakeup_seq(%rdi), %r9
	movl	broadcast_seq(%rdi), %edx
	movq	%r9, 24(%rsp)
	movl	%edx, 4(%rsp)

	/* Unlock.  */
8:	movl	cond_futex(%rdi), %edx
	LOCK
#if cond_lock == 0
	decl	(%rdi)
#else
	decl	cond_lock(%rdi)
#endif
	jne	3f

.LcleanupSTART:
4:	callq	__pthread_enable_asynccancel
	movl	%eax, (%rsp)

	xorq	%r10, %r10
	LP_OP(cmp) $-1, dep_mutex(%rdi)
	leaq	cond_futex(%rdi), %rdi
	movl	$FUTEX_WAIT, %esi
	je	60f

	mov	dep_mutex-cond_futex(%rdi), %R8_LP
	/* Requeue to a non-robust PI mutex if the PI bit is set and
	the robust bit is not set.  */
	movl	MUTEX_KIND(%r8), %eax
	andl	$(ROBUST_BIT|PI_BIT), %eax
	cmpl	$PI_BIT, %eax
	jne	61f

	movl	$(FUTEX_WAIT_REQUEUE_PI|FUTEX_PRIVATE_FLAG), %esi
	movl	$SYS_futex, %eax
	syscall

	cmpl	$0, %eax
	sete	%r8b

#ifdef __ASSUME_REQUEUE_PI
	jmp	62f
#else
	je	62f

	/* When a futex syscall with FUTEX_WAIT_REQUEUE_PI returns
	   successfully, it has already locked the mutex for us and the
	   pi_flag (%r8b) is set to denote that fact.  However, if another
	   thread changed the futex value before we entered the wait, the
	   syscall may return an EAGAIN and the mutex is not locked.  We go
	   ahead with a success anyway since later we look at the pi_flag to
	   decide if we got the mutex or not.  The sequence numbers then make
	   sure that only one of the threads actually wake up.  We retry using
	   normal FUTEX_WAIT only if the kernel returned ENOSYS, since normal
	   and PI futexes don't mix.

	   Note that we don't check for EAGAIN specifically; we assume that the
	   only other error the futex function could return is EAGAIN since
	   anything else would mean an error in our function.  It is too
	   expensive to do that check for every call (which is 	quite common in
	   case of a large number of threads), so it has been skipped.  */
	cmpl	$-ENOSYS, %eax
	jne	62f

# ifndef __ASSUME_PRIVATE_FUTEX
	movl	$FUTEX_WAIT, %esi
# endif
#endif

61:
#ifdef __ASSUME_PRIVATE_FUTEX
	movl	$(FUTEX_WAIT|FUTEX_PRIVATE_FLAG), %esi
#else
	orl	%fs:PRIVATE_FUTEX, %esi
#endif
60:	xorb	%r8b, %r8b
	movl	$SYS_futex, %eax
	syscall

62:	movl	(%rsp), %edi
	callq	__pthread_disable_asynccancel
.LcleanupEND:

	/* Lock.  */
	movq	8(%rsp), %rdi
	movl	$1, %esi
	xorl	%eax, %eax
	LOCK
#if cond_lock == 0
	cmpxchgl %esi, (%rdi)
#else
	cmpxchgl %esi, cond_lock(%rdi)
#endif
	jnz	5f

6:	movl	broadcast_seq(%rdi), %edx

	movq	woken_seq(%rdi), %rax

	movq	wakeup_seq(%rdi), %r9

	cmpl	4(%rsp), %edx
	jne	16f

	cmpq	24(%rsp), %r9
	jbe	19f

	cmpq	%rax, %r9
	jna	19f

	incq	woken_seq(%rdi)

	/* Unlock */
16:	subl	$(1 << nwaiters_shift), cond_nwaiters(%rdi)

	/* Wake up a thread which wants to destroy the condvar object.  */
	cmpq	$0xffffffffffffffff, total_seq(%rdi)
	jne	17f
	movl	cond_nwaiters(%rdi), %eax
	andl	$~((1 << nwaiters_shift) - 1), %eax
	jne	17f

	addq	$cond_nwaiters, %rdi
	LP_OP(cmp) $-1, dep_mutex-cond_nwaiters(%rdi)
	movl	$1, %edx
#ifdef __ASSUME_PRIVATE_FUTEX
	movl	$FUTEX_WAKE, %eax
	movl	$(FUTEX_WAKE|FUTEX_PRIVATE_FLAG), %esi
	cmove	%eax, %esi
#else
	movl	$0, %eax
	movl	%fs:PRIVATE_FUTEX, %esi
	cmove	%eax, %esi
	orl	$FUTEX_WAKE, %esi
#endif
	movl	$SYS_futex, %eax
	syscall
	subq	$cond_nwaiters, %rdi

17:	LOCK
#if cond_lock == 0
	decl	(%rdi)
#else
	decl	cond_lock(%rdi)
#endif
	jne	10f

	/* If requeue_pi is used the kernel performs the locking of the
	   mutex. */
11:	movq	16(%rsp), %rdi
	testb	%r8b, %r8b
	jnz	18f

	callq	__pthread_mutex_cond_lock

14:	leaq	FRAME_SIZE(%rsp), %rsp
	cfi_adjust_cfa_offset(-FRAME_SIZE)

	/* We return the result of the mutex_lock operation.  */
	retq

	cfi_adjust_cfa_offset(FRAME_SIZE)

18:	callq	__pthread_mutex_cond_lock_adjust
	xorl	%eax, %eax
	jmp	14b

	/* We need to go back to futex_wait.  If we're using requeue_pi, then
	   release the mutex we had acquired and go back.  */
19:	testb	%r8b, %r8b
	jz	8b

	/* Adjust the mutex values first and then unlock it.  The unlock
	   should always succeed or else the kernel did not lock the mutex
	   correctly.  */
	movq	16(%rsp), %rdi
	callq	__pthread_mutex_cond_lock_adjust
	movq	%rdi, %r8
	xorl	%esi, %esi
	callq	__pthread_mutex_unlock_usercnt
	/* Reload cond_var.  */
	movq	8(%rsp), %rdi
	jmp	8b

	/* Initial locking failed.  */
1:
#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
	jmp	2b

	/* Unlock in loop requires wakeup.  */
3:
#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
	jmp	4b

	/* Locking in loop failed.  */
5:
#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
	jmp	6b

	/* Unlock after loop requires wakeup.  */
10:
#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_unlock_wake
	jmp	11b

	/* The initial unlocking of the mutex failed.  */
12:	movq	%rax, %r10
	movq	8(%rsp), %rdi
	LOCK
#if cond_lock == 0
	decl	(%rdi)
#else
	decl	cond_lock(%rdi)
#endif
	je	13f

#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_unlock_wake

13:	movq	%r10, %rax
	jmp	14b

	.size	__pthread_cond_wait, .-__pthread_cond_wait
versioned_symbol (libpthread, __pthread_cond_wait, pthread_cond_wait,
		  GLIBC_2_3_2)


	.align	16
	.type	__condvar_cleanup1, @function
	.globl	__condvar_cleanup1
	.hidden	__condvar_cleanup1
__condvar_cleanup1:
	/* Stack frame:

	   rsp + 32
		    +--------------------------+
	   rsp + 24 | unused                   |
		    +--------------------------+
	   rsp + 16 | mutex pointer            |
		    +--------------------------+
	   rsp +  8 | condvar pointer          |
		    +--------------------------+
	   rsp +  4 | old broadcast_seq value  |
		    +--------------------------+
	   rsp +  0 | old cancellation mode    |
		    +--------------------------+
	*/

	movq	%rax, 24(%rsp)

	/* Get internal lock.  */
	movq	8(%rsp), %rdi
	movl	$1, %esi
	xorl	%eax, %eax
	LOCK
#if cond_lock == 0
	cmpxchgl %esi, (%rdi)
#else
	cmpxchgl %esi, cond_lock(%rdi)
#endif
	jz	1f

#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

1:	movl	broadcast_seq(%rdi), %edx
	cmpl	4(%rsp), %edx
	jne	3f

	/* We increment the wakeup_seq counter only if it is lower than
	   total_seq.  If this is not the case the thread was woken and
	   then canceled.  In this case we ignore the signal.  */
	movq	total_seq(%rdi), %rax
	cmpq	wakeup_seq(%rdi), %rax
	jbe	6f
	incq	wakeup_seq(%rdi)
	incl	cond_futex(%rdi)
6:	incq	woken_seq(%rdi)

3:	subl	$(1 << nwaiters_shift), cond_nwaiters(%rdi)

	/* Wake up a thread which wants to destroy the condvar object.  */
	xorl	%ecx, %ecx
	cmpq	$0xffffffffffffffff, total_seq(%rdi)
	jne	4f
	movl	cond_nwaiters(%rdi), %eax
	andl	$~((1 << nwaiters_shift) - 1), %eax
	jne	4f

	LP_OP(cmp) $-1, dep_mutex(%rdi)
	leaq	cond_nwaiters(%rdi), %rdi
	movl	$1, %edx
#ifdef __ASSUME_PRIVATE_FUTEX
	movl	$FUTEX_WAKE, %eax
	movl	$(FUTEX_WAKE|FUTEX_PRIVATE_FLAG), %esi
	cmove	%eax, %esi
#else
	movl	$0, %eax
	movl	%fs:PRIVATE_FUTEX, %esi
	cmove	%eax, %esi
	orl	$FUTEX_WAKE, %esi
#endif
	movl	$SYS_futex, %eax
	syscall
	subq	$cond_nwaiters, %rdi
	movl	$1, %ecx

4:	LOCK
#if cond_lock == 0
	decl	(%rdi)
#else
	decl	cond_lock(%rdi)
#endif
	je	2f
#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 %rcx.  */
	callq	__lll_unlock_wake

	/* Wake up all waiters to make sure no signal gets lost.  */
2:	testl	%ecx, %ecx
	jnz	5f
	addq	$cond_futex, %rdi
	LP_OP(cmp) $-1, dep_mutex-cond_futex(%rdi)
	movl	$0x7fffffff, %edx
#ifdef __ASSUME_PRIVATE_FUTEX
	movl	$FUTEX_WAKE, %eax
	movl	$(FUTEX_WAKE|FUTEX_PRIVATE_FLAG), %esi
	cmove	%eax, %esi
#else
	movl	$0, %eax
	movl	%fs:PRIVATE_FUTEX, %esi
	cmove	%eax, %esi
	orl	$FUTEX_WAKE, %esi
#endif
	movl	$SYS_futex, %eax
	syscall

	/* Lock the mutex only if we don't own it already.  This only happens
	   in case of PI mutexes, if we got cancelled after a successful
	   return of the futex syscall and before disabling async
	   cancellation.  */
5:	movq	16(%rsp), %rdi
	movl	MUTEX_KIND(%rdi), %eax
	andl	$(ROBUST_BIT|PI_BIT), %eax
	cmpl	$PI_BIT, %eax
	jne	7f

	movl	(%rdi), %eax
	andl	$TID_MASK, %eax
	cmpl	%eax, %fs:TID
	jne	7f
	/* We managed to get the lock.  Fix it up before returning.  */
	callq	__pthread_mutex_cond_lock_adjust
	jmp	8f


7:	callq	__pthread_mutex_cond_lock

8:	movq	24(%rsp), %rdi
.LcallUR:
	call	_Unwind_Resume@PLT
	hlt
.LENDCODE:
	cfi_endproc
	.size	__condvar_cleanup1, .-__condvar_cleanup1


	.section .gcc_except_table,"a",@progbits
.LexceptSTART:
	.byte	DW_EH_PE_omit			# @LPStart format
	.byte	DW_EH_PE_omit			# @TType format
	.byte	DW_EH_PE_uleb128		# call-site format
	.uleb128 .Lcstend-.Lcstbegin
.Lcstbegin:
	.uleb128 .LcleanupSTART-.LSTARTCODE
	.uleb128 .LcleanupEND-.LcleanupSTART
	.uleb128 __condvar_cleanup1-.LSTARTCODE
	.uleb128 0
	.uleb128 .LcallUR-.LSTARTCODE
	.uleb128 .LENDCODE-.LcallUR
	.uleb128 0
	.uleb128 0
.Lcstend:


#ifdef SHARED
	.hidden	DW.ref.__gcc_personality_v0
	.weak	DW.ref.__gcc_personality_v0
	.section .gnu.linkonce.d.DW.ref.__gcc_personality_v0,"aw",@progbits
	.align	LP_SIZE
	.type	DW.ref.__gcc_personality_v0, @object
	.size	DW.ref.__gcc_personality_v0, LP_SIZE
DW.ref.__gcc_personality_v0:
	ASM_ADDR __gcc_personality_v0
#endif