[Android] [PATCH] Add pthread_once function from AOSP

[Rafaël Carré]

Le 28/06/2012 12:37, Edward Wang a écrit :
> On 12-06-28 04:55 AM, Rafaël Carré <funman at videolan.org> wrote:
>> Le 28/06/2012 00:09, Edward Wang a écrit :
>>> See:
>>> http://www.compdigitec.com/labs/2012/06/25/fclose-freezes-when-run-inside-pthread-on-android-2-1/
>>> http://code.google.com/p/android/issues/detail?id=5116
>>>
>>> Summary:
>>> Android 2.1/2.2's pthread implementation has a bug where fclose() hangs inside pthread. This commit imports a working version of pthread_once that makes VLC for Android work on Android 2.1 and 2.2.
>>> ---
>>>   Updated version, please discard previous version.
>>>
>>>   vlc-android/jni/Android.mk     |    3 +-
>>>   vlc-android/jni/pthread-once.c |   91 ++++++++++++++++++++++++++++++++++++++++
>>>   2 files changed, 93 insertions(+), 1 deletions(-)
>>>   create mode 100644 vlc-android/jni/pthread-once.c
>>>
>>> diff --git a/vlc-android/jni/Android.mk b/vlc-android/jni/Android.mk
>>> index 7c05cb5..b2647d4 100644
>>> --- a/vlc-android/jni/Android.mk
>>> +++ b/vlc-android/jni/Android.mk
>>> @@ -3,7 +3,7 @@ include $(CLEAR_VARS)
>>>
>>>   LOCAL_MODULE    := libvlcjni
>>>
>>> -LOCAL_SRC_FILES := libvlcjni.c aout.c thumbnailer.c pthread-condattr.c pthread-rwlocks.c eventfd.c sem.c
>>> +LOCAL_SRC_FILES := libvlcjni.c aout.c thumbnailer.c pthread-condattr.c pthread-rwlocks.c pthread-once.c eventfd.c sem.c
>>>
>>>   LOCAL_C_INCLUDES := $(VLC_SRC_DIR)/include
>>>
>>> @@ -11,6 +11,7 @@ ARCH=$(ANDROID_ABI)
>>>
>>>   CPP_STATIC=$(ANDROID_NDK)/sources/cxx-stl/gnu-libstdc++/libs/$(ARCH)/libgnustl_static.a
>>>
>>> +LOCAL_ARM_MODE := arm
>> not related?
> It is related, please see below:
>>>   LOCAL_CFLAGS := -std=gnu99
>>>   ifeq ($(ARCH), "armeabi")
>>>   	LOCAL_CFLAGS += -DHAVE_ARMEABI
>>> diff --git a/vlc-android/jni/pthread-once.c b/vlc-android/jni/pthread-once.c
>>> new file mode 100644
>>> index 0000000..0fae403
>>> --- /dev/null
>>> +++ b/vlc-android/jni/pthread-once.c
>>> @@ -0,0 +1,91 @@
>>> +/*
>>> + * Copyright (C) 2008 The Android Open Source Project
>>> + * All rights reserved.
>>> + *
>>> + * Redistribution and use in source and binary forms, with or without
>>> + * modification, are permitted provided that the following conditions
>>> + * are met:
>>> + *  * Redistributions of source code must retain the above copyright
>>> + *    notice, this list of conditions and the following disclaimer.
>>> + *  * Redistributions in binary form must reproduce the above copyright
>>> + *    notice, this list of conditions and the following disclaimer in
>>> + *    the documentation and/or other materials provided with the
>>> + *    distribution.
>>> + *
>>> + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
>>> + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
>>> + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
>>> + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
>>> + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
>>> + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
>>> + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
>>> + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
>>> + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
>>> + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
>>> + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
>>> + * SUCH DAMAGE.
>>> + */
>>> +#include<errno.h>
>>> +#include<pthread.h>
>>> +#include<unistd.h>
>>> +
>>> +#include<machine/cpu-features.h>
>>> +
>>> +/* Adapted from bionic_atomic_inline.h */
>>> +void ANDROID_MEMBAR_FULL() {
>>> +    if(sysconf(_SC_NPROCESSORS_CONF)>  1) { /* SMP */
>> no need to detect SMP at runtime, just use the same code everywhere and
>> asm ("" : : : "memory") as fallback
> OK
>>
>>> +#ifdef __arm__
>>> +    #if __ARM_ARCH__>= 7
>>> +            do { __asm__ __volatile__ ("dmb" ::: "memory"); } while (0);
>>> +    #elif __ARM_ARCH__ == 6
>>> +            /*
>>> +            * For ARMv6 we need to issue a specific MCR instead of the DMB, since
>>> +            * that wasn't added until v7.
>>> +            */
>>> +            do { __asm__ __volatile__ ("mcr p15, 0, %0, c7, c10, 5" :: "r" (0) : "memory"); } while (0);
>> Is the system control coprocessor present on all ARMv6 ?
> It is present in ARMv6 base in _ARM_ mode, that's why I had 
> LOCAL_MODE_ARM set above to ensure it runs on all ARMv6 devices.


The coprocessor is always present or always absent, it doesn't depend of
the current thumb mode or not.

In thumb 16 bits mode you can not use mcr instructions, however in
thumb-2 you can.

ARM/Thumb2 quick reference card:
http://infocenter.arm.com/help/topic/com.arm.doc.qrc0001l/QRC0001_UAL.pdf
Thumb1 quick reference card:
http://web.eecs.umich.edu/~prabal/teaching/eecs373-f10/readings/ARM_QRC0006_UAL16.pdf


Since we have CPUs < ARMv6T2 we should use thumb1 on ARMv6 but on
anything newer we can use Thumb2 and thus we don't need ARM mode, so
please make that +LOCAL_ARM_MODE := arm depend on ANDROID_ABI=armeabi
and add a comment.



I checked that cp15 is always present on >= ARMv6 (it was optional for
previous architectures although often present):

http://www.scss.tcd.ie/~waldroj/3d1/arm_arm.pdf :
Prior to ARMv6, the System Control coprocessor (CP15) described in
Chapter B3 was a
recommendation only. Support for this coprocessor is now mandated in ARMv6.