Unified header system doesn't provide pthread_mutex_lock_timeout_np

[Tapped]

Description

usr/include/pthread.h in the unified sysroot folder doesn't have pthread_mutex_lock_timeout_np, which was the standard way to lock a mutex with timeout on platforms less than android-21. Now the only method to lock a mutex with timeout is pthread_mutex_timedlock which is only available in android-21 and above. I suspect this is a bug with the unified header system, which I would expect to provide pthread_mutex_lock_timeout_np for __ANDROID_API__ < 21. Right now there is no way to target versions less than android-21 that uses a system based mutex lock with timeout.

We have made a workaround (that still uses the unified header system) for it, that emulates the behavior, but is probably slower than what the kernel can provide.

    long long timeout = get_ticks() + millisecondsTimeout * 10000ll;
    while (pthread_mutex_trylock(mutexHandle) == EBUSY)
    {
        long long now = get_ticks(); // Replace get_ticks with your method for getting CPU ticks.
        if (now >= timeout)
            return false;

        pthread_yield();
    }
    return true;

Environment Details

• NDK Version: 15.0.4075724
• Build system: Gradle - CMake
• Host OS: Windows and macOS
• Compiler: Clang
• ABI: armeabi-v7a
• STL: libstlport
• NDK API level: android-16

[DanAlbert]

The fix has been merged into r15b. I'm sending build 4113355 of ndk-r15-release off to QA here in a bit if you want to grab the RC from the build server (https://android.googlesource.com/platform/ndk/+/master/docs/ContinuousBuilds.md), otherwise it should be out some time this week.

[rcdailey]

@DanAlbert: I just installed build from here:

https://partner.android.com/build#p:id=builddetail&pp=branch%253Daosp-ndk-r15-release%2526buildnumber%253D4119039%2526target%253Dwin64&a=100621237

This does not seem to fix my problem. Boost Thread isn't able to find it:

In file included from E:/code/frontend/source/Core/ThirdParty/boost/include\boost/thread/mutex.hpp:16:

E:/code/frontend/source/Core/ThirdParty/boost/include\boost/thread/pthread/mutex.hpp:251:25: error: use of undeclared identifier 'pthread_mutex_timedlock'

          int const res=pthread_mutex_timedlock(&m,&timeout);

                        ^

I'm using API 15. This worked fine when I wasn't using the unified headers. What do I need to do to get this working again?

[DanAlbert]

That code shouldn't work for either set of headers if you're targeting API 15 (it should work for 64-bit ABIs, but that's because 15 should be translated to 21 for those). pthread_mutex_timedlock didn't exist until android-21.

What ABI are you targeting, and what build system are you using?

[DanAlbert]

The check in boost looks fine: https://github.com/boostorg/thread/blob/develop/include/boost/thread/pthread/mutex.hpp#L30

Are you manually passing -DBOOST_PTHREAD_HAS_TIMEDLOCK or something?

[rcdailey]

Using CMake 3.8.1. ABI is armeabi-v7a. My CMake toolchain is below:

set( CMAKE_SYSTEM_NAME Android )
set( CMAKE_SYSTEM_VERSION 15 ) # API level
set( CMAKE_ANDROID_ARCH_ABI armeabi-v7a )
set( CMAKE_ANDROID_STL_TYPE gnustl_shared )
set( CMAKE_ANDROID_NDK_TOOLCHAIN_VERSION clang )
set( CMAKE_ANDROID_NDK_DEPRECATED_HEADERS 1 )

[rcdailey]

@DanAlbert I'm not specifying that compiler definition myself. But in boost/thread/pthread/mutex.hpp it does this at the top:

#if (defined(_POSIX_TIMEOUTS) && (_POSIX_TIMEOUTS-0)>=200112L) \
 || (defined(__ANDROID__) && defined(__ANDROID_API__) && __ANDROID_API__ >= 21)
#ifndef BOOST_PTHREAD_HAS_TIMEDLOCK
#define BOOST_PTHREAD_HAS_TIMEDLOCK
#endif
#endif

Could this be the cause?

[DanAlbert]

No, that check is fine. The first half of the or fails because _POSIX_TIMEOUTS-0 will be -1 unless you're targeting android-21+ https://android.googlesource.com/platform/bionic/+/master/libc/include/bits/posix_limits.h#108

The second half is fine because you're not targeting 21+, so neither case should be true, and it shouldn't be defined.

Can you provide the failing compilation command? The clang++ command from the log (ninja -v if you're using ninja, pass -DCMAKE_VERBOSE_MAKEFILE=ON when running cmake if you're using make, idk what for anything else)

[alexcohn]

@DanAlbert As I showed in #423, this patch is not enough. Please supply all defines and functions that were declared in pthread.h before android-21.

[enh]

i don't think that's true... i built boost with just that patch (with https://gist.github.com/enh/b2dc8e2cbbce7fffffde2135271b10fd and a locally modified toolchain).

[enh]

yeah, boost 1.64.0 builds fine for me if i replace my hacked r15 with clean r15b (though note that the bootstrap step requires that "clang" is a working host clang, so i had to have a symlink to /usr/bin/clang-3.8 on my ubuntu box).

[rcdailey]

I'm using boost 1.63. I'll get you the command invocation later.

[DanAlbert]

@alexcohn: sorry for missing all the details in the other bug, I've uploaded a change to re-expose some more legacy APIs. That should actually be affecting this bug though because the missing API here is the one we did expose.

@rcdailey: Alright, please do. That should help figure out what's going on.

[rcdailey]

@DanAlbert I must have had some other issue, because I'm not able to reproduce this anymore. Sorry for the confusion. This looks to be working fine under API 15.