[llvm] r211287 - Remove support for LLVM runtime multi-threading.
Zachary Turner
zturner at google.com
Fri Jun 20 10:26:08 PDT 2014
It's odd that I'm not able to reproduce this. I'm also using MSVC and I
run cmake as
cmake -D LLVM_ENABLE_THREADS:BOOL=OFF
Is this what you're doing, or do you have some other options set?
On Fri, Jun 20, 2014 at 10:04 AM, Yaron Keren <yaron.keren at gmail.com> wrote:
> No, I had not verified this yet, just hoped it may ring a bell.
> I'll try revisions.
>
> Yaron
>
>
>
> 2014-06-20 19:54 GMT+03:00 Zachary Turner <zturner at google.com>:
>
> I am trying to reproduce locally as well.
>
>
>
> On Fri, Jun 20, 2014 at 9:52 AM, Zachary Turner <zturner at google.com>
> wrote:
>
>> Did you verify that it's this revision specifically that caused it? Can
>> you just checkout the revision immediately before this and confirm it
>> works, and then checkout this revision and confirm it doesn't work? I
>> suspect it's actually a different revision that caused it, since these
>> functions were actually just no-ops at this point.
>>
>>
>> On Fri, Jun 20, 2014 at 9:46 AM, Yaron Keren <yaron.keren at gmail.com>
>> wrote:
>>
>>> Running ARCMT clang tests with these two tools stopped working for me
>>> after updating to trunk today, on WIndows 64 bit Visual C++ 2013 building
>>> 32 bit target. They just hang and never finish. I thought initially that's
>>> related to them running in thread but the same happens even if the thread
>>> is disabled in main() and cindextest_main() is called directly.
>>> llvm tests complete OK as are other clang tests that do not use c-arcmt-test
>>> and and c-index-test.
>>>
>>> It this possibly related to mutex changes?
>>> Maybe LLVM must be built with threads to support the ARCMT tests?
>>>
>>> Yaron
>>>
>>>
>>>
>>>
>>> 2014-06-20 19:40 GMT+03:00 Zachary Turner <zturner at google.com>:
>>>
>>> It should continue to work. The only thing llvm_start_multithreaded()
>>>> and llvm_stop_multithreaded() did before, despite their names, was to
>>>> allocate a mutex on the heap that served as a global lock. In other words,
>>>> it didn't really do much of anything useful. You could still create
>>>> threads even if you compiled with LLVM_ENABLE_THREADS=0. Some stuff might
>>>> not have been safe for concurrent access, but a) that's not an issue with
>>>> these tests anyway, since they create the thread and then join, so there is
>>>> no concurrency, and b) the areas that were conditionally protected by this
>>>> global lock before are now always protected.
>>>>
>>>> In fact, this makes me wonder if we even need the compile time flag.
>>>>
>>>
>>>
>>> On Fri, Jun 20, 2014 at 9:34 AM, Yaron Keren <yaron.keren at gmail.com>
>>> wrote:
>>>
>>>> Hi,
>>>>
>>>> Two of the clang test tools, c-arcmt-test and and c-index-test always
>>>> run the test through one thread only:
>>>>
>>>> /* We intentionally run in a separate thread to ensure we at least
>>>> minimal
>>>> * testing of a multithreaded environment (for example, having a
>>>> reduced stack
>>>> * size). */
>>>>
>>>> If LLVM/clang were built without thread support, can these tools
>>>> continue the same?
>>>>
>>>> Yaron
>>>>
>>>>
>>>>
>>>>
>>>> 2014-06-19 21:18 GMT+03:00 Zachary Turner <zturner at google.com>:
>>>>
>>>>> Author: zturner
>>>>> Date: Thu Jun 19 13:18:23 2014
>>>>> New Revision: 211287
>>>>>
>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=211287&view=rev
>>>>> Log:
>>>>> Remove support for LLVM runtime multi-threading.
>>>>>
>>>>> After a number of previous small iterations, the functions
>>>>> llvm_start_multithreaded() and llvm_stop_multithreaded() have
>>>>> been reduced essentially to no-ops. This change removes them
>>>>> entirely.
>>>>>
>>>>> Reviewed by: rnk, dblaikie
>>>>>
>>>>> Differential Revision: http://reviews.llvm.org/D4216
>>>>>
>>>>> Modified:
>>>>> llvm/trunk/docs/ProgrammersManual.rst
>>>>> llvm/trunk/include/llvm-c/Core.h
>>>>> llvm/trunk/include/llvm/Support/ManagedStatic.h
>>>>> llvm/trunk/include/llvm/Support/Threading.h
>>>>> llvm/trunk/lib/IR/Core.cpp
>>>>> llvm/trunk/lib/Support/Threading.cpp
>>>>> llvm/trunk/unittests/Support/ManagedStatic.cpp
>>>>>
>>>>> Modified: llvm/trunk/docs/ProgrammersManual.rst
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/ProgrammersManual.rst?rev=211287&r1=211286&r2=211287&view=diff
>>>>>
>>>>> ==============================================================================
>>>>> --- llvm/trunk/docs/ProgrammersManual.rst (original)
>>>>> +++ llvm/trunk/docs/ProgrammersManual.rst Thu Jun 19 13:18:23 2014
>>>>> @@ -2170,46 +2170,13 @@ compiler, consider compiling LLVM and LL
>>>>> using the resultant compiler to build a copy of LLVM with
>>>>> multithreading
>>>>> support.
>>>>>
>>>>> -.. _startmultithreaded:
>>>>> -
>>>>> -Entering and Exiting Multithreaded Mode
>>>>> ----------------------------------------
>>>>> -
>>>>> -In order to properly protect its internal data structures while
>>>>> avoiding
>>>>> -excessive locking overhead in the single-threaded case, the LLVM must
>>>>> intialize
>>>>> -certain data structures necessary to provide guards around its
>>>>> internals. To do
>>>>> -so, the client program must invoke ``llvm_start_multithreaded()``
>>>>> before making
>>>>> -any concurrent LLVM API calls. To subsequently tear down these
>>>>> structures, use
>>>>> -the ``llvm_stop_multithreaded()`` call. You can also use the
>>>>> -``llvm_is_multithreaded()`` call to check the status of multithreaded
>>>>> mode.
>>>>> -
>>>>> -Note that both of these calls must be made *in isolation*. That is
>>>>> to say that
>>>>> -no other LLVM API calls may be executing at any time during the
>>>>> execution of
>>>>> -``llvm_start_multithreaded()`` or ``llvm_stop_multithreaded``. It is
>>>>> the
>>>>> -client's responsibility to enforce this isolation.
>>>>> -
>>>>> -The return value of ``llvm_start_multithreaded()`` indicates the
>>>>> success or
>>>>> -failure of the initialization. Failure typically indicates that your
>>>>> copy of
>>>>> -LLVM was built without multithreading support, typically because GCC
>>>>> atomic
>>>>> -intrinsics were not found in your system compiler. In this case, the
>>>>> LLVM API
>>>>> -will not be safe for concurrent calls. However, it *will* be safe
>>>>> for hosting
>>>>> -threaded applications in the JIT, though :ref:`care must be taken
>>>>> -<jitthreading>` to ensure that side exits and the like do not
>>>>> accidentally
>>>>> -result in concurrent LLVM API calls.
>>>>> -
>>>>> .. _shutdown:
>>>>>
>>>>> Ending Execution with ``llvm_shutdown()``
>>>>> -----------------------------------------
>>>>>
>>>>> When you are done using the LLVM APIs, you should call
>>>>> ``llvm_shutdown()`` to
>>>>> -deallocate memory used for internal structures. This will also invoke
>>>>> -``llvm_stop_multithreaded()`` if LLVM is operating in multithreaded
>>>>> mode. As
>>>>> -such, ``llvm_shutdown()`` requires the same isolation guarantees as
>>>>> -``llvm_stop_multithreaded()``.
>>>>> -
>>>>> -Note that, if you use scope-based shutdown, you can use the
>>>>> -``llvm_shutdown_obj`` class, which calls ``llvm_shutdown()`` in its
>>>>> destructor.
>>>>> +deallocate memory used for internal structures.
>>>>>
>>>>> .. _managedstatic:
>>>>>
>>>>> @@ -2217,15 +2184,11 @@ Lazy Initialization with ``ManagedStatic
>>>>> ------------------------------------------
>>>>>
>>>>> ``ManagedStatic`` is a utility class in LLVM used to implement static
>>>>> -initialization of static resources, such as the global type tables.
>>>>> Before the
>>>>> -invocation of ``llvm_shutdown()``, it implements a simple lazy
>>>>> initialization
>>>>> -scheme. Once ``llvm_start_multithreaded()`` returns, however, it uses
>>>>> +initialization of static resources, such as the global type tables.
>>>>> In a
>>>>> +single-threaded environment, it implements a simple lazy
>>>>> initialization scheme.
>>>>> +When LLVM is compiled with support for multi-threading, however, it
>>>>> uses
>>>>> double-checked locking to implement thread-safe lazy initialization.
>>>>>
>>>>> -Note that, because no other threads are allowed to issue LLVM API
>>>>> calls before
>>>>> -``llvm_start_multithreaded()`` returns, it is possible to have
>>>>> -``ManagedStatic``\ s of ``llvm::sys::Mutex``\ s.
>>>>> -
>>>>> .. _llvmcontext:
>>>>>
>>>>> Achieving Isolation with ``LLVMContext``
>>>>>
>>>>> Modified: llvm/trunk/include/llvm-c/Core.h
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm-c/Core.h?rev=211287&r1=211286&r2=211287&view=diff
>>>>>
>>>>> ==============================================================================
>>>>> --- llvm/trunk/include/llvm-c/Core.h (original)
>>>>> +++ llvm/trunk/include/llvm-c/Core.h Thu Jun 19 13:18:23 2014
>>>>> @@ -2848,16 +2848,13 @@ void LLVMDisposePassManager(LLVMPassMana
>>>>> * @{
>>>>> */
>>>>>
>>>>> -/** Allocate and initialize structures needed to make LLVM safe for
>>>>> - multithreading. The return value indicates whether multithreaded
>>>>> - initialization succeeded. Must be executed in isolation from all
>>>>> - other LLVM api calls.
>>>>> - @see llvm::llvm_start_multithreaded */
>>>>> +/** Deprecated: Multi-threading can only be enabled/disabled with the
>>>>> compile
>>>>> + time define LLVM_ENABLE_THREADS. This function always returns
>>>>> + LLVMIsMultithreaded(). */
>>>>> LLVMBool LLVMStartMultithreaded(void);
>>>>>
>>>>> -/** Deallocate structures necessary to make LLVM safe for
>>>>> multithreading.
>>>>> - Must be executed in isolation from all other LLVM api calls.
>>>>> - @see llvm::llvm_stop_multithreaded */
>>>>> +/** Deprecated: Multi-threading can only be enabled/disabled with the
>>>>> compile
>>>>> + time define LLVM_ENABLE_THREADS. */
>>>>> void LLVMStopMultithreaded(void);
>>>>>
>>>>> /** Check whether LLVM is executing in thread-safe mode or not.
>>>>>
>>>>> Modified: llvm/trunk/include/llvm/Support/ManagedStatic.h
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/ManagedStatic.h?rev=211287&r1=211286&r2=211287&view=diff
>>>>>
>>>>> ==============================================================================
>>>>> --- llvm/trunk/include/llvm/Support/ManagedStatic.h (original)
>>>>> +++ llvm/trunk/include/llvm/Support/ManagedStatic.h Thu Jun 19
>>>>> 13:18:23 2014
>>>>> @@ -103,9 +103,6 @@ void llvm_shutdown();
>>>>> /// llvm_shutdown() when it is destroyed.
>>>>> struct llvm_shutdown_obj {
>>>>> llvm_shutdown_obj() { }
>>>>> - explicit llvm_shutdown_obj(bool multithreaded) {
>>>>> - if (multithreaded) llvm_start_multithreaded();
>>>>> - }
>>>>> ~llvm_shutdown_obj() { llvm_shutdown(); }
>>>>> };
>>>>>
>>>>>
>>>>> Modified: llvm/trunk/include/llvm/Support/Threading.h
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Threading.h?rev=211287&r1=211286&r2=211287&view=diff
>>>>>
>>>>> ==============================================================================
>>>>> --- llvm/trunk/include/llvm/Support/Threading.h (original)
>>>>> +++ llvm/trunk/include/llvm/Support/Threading.h Thu Jun 19 13:18:23
>>>>> 2014
>>>>> @@ -7,30 +7,19 @@
>>>>> //
>>>>>
>>>>> //===----------------------------------------------------------------------===//
>>>>> //
>>>>> -// TThis file defines llvm_start_multithreaded() and friends.
>>>>> +// This file declares helper functions for running LLVM in a
>>>>> multi-threaded
>>>>> +// environment.
>>>>> //
>>>>>
>>>>> //===----------------------------------------------------------------------===//
>>>>>
>>>>> #ifndef LLVM_SUPPORT_THREADING_H
>>>>> #define LLVM_SUPPORT_THREADING_H
>>>>>
>>>>> -namespace llvm {
>>>>> - /// llvm_start_multithreaded - Allocate and initialize structures
>>>>> needed to
>>>>> - /// make LLVM safe for multithreading. The return value indicates
>>>>> whether
>>>>> - /// multithreaded initialization succeeded. LLVM will still be
>>>>> operational
>>>>> - /// on "failed" return, and will still be safe for hosting threading
>>>>> - /// applications in the JIT, but will not be safe for concurrent
>>>>> calls to the
>>>>> - /// LLVM APIs.
>>>>> - /// THIS MUST EXECUTE IN ISOLATION FROM ALL OTHER LLVM API CALLS.
>>>>> - bool llvm_start_multithreaded();
>>>>> -
>>>>> - /// llvm_stop_multithreaded - Deallocate structures necessary to
>>>>> make LLVM
>>>>> - /// safe for multithreading.
>>>>> - /// THIS MUST EXECUTE IN ISOLATION FROM ALL OTHER LLVM API CALLS.
>>>>> - void llvm_stop_multithreaded();
>>>>> +#include "llvm/Support/Mutex.h"
>>>>>
>>>>> - /// llvm_is_multithreaded - Check whether LLVM is executing in
>>>>> thread-safe
>>>>> - /// mode or not.
>>>>> +namespace llvm {
>>>>> + /// Returns true if LLVM is compiled with support for
>>>>> multi-threading, and
>>>>> + /// false otherwise.
>>>>> bool llvm_is_multithreaded();
>>>>>
>>>>> /// llvm_execute_on_thread - Execute the given \p UserFn on a
>>>>> separate
>>>>>
>>>>> Modified: llvm/trunk/lib/IR/Core.cpp
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Core.cpp?rev=211287&r1=211286&r2=211287&view=diff
>>>>>
>>>>> ==============================================================================
>>>>> --- llvm/trunk/lib/IR/Core.cpp (original)
>>>>> +++ llvm/trunk/lib/IR/Core.cpp Thu Jun 19 13:18:23 2014
>>>>> @@ -2702,11 +2702,10 @@ void LLVMDisposePassManager(LLVMPassMana
>>>>> /*===-- Threading
>>>>> ------------------------------------------------------===*/
>>>>>
>>>>> LLVMBool LLVMStartMultithreaded() {
>>>>> - return llvm_start_multithreaded();
>>>>> + return LLVMIsMultithreaded();
>>>>> }
>>>>>
>>>>> void LLVMStopMultithreaded() {
>>>>> - llvm_stop_multithreaded();
>>>>> }
>>>>>
>>>>> LLVMBool LLVMIsMultithreaded() {
>>>>>
>>>>> Modified: llvm/trunk/lib/Support/Threading.cpp
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Threading.cpp?rev=211287&r1=211286&r2=211287&view=diff
>>>>>
>>>>> ==============================================================================
>>>>> --- llvm/trunk/lib/Support/Threading.cpp (original)
>>>>> +++ llvm/trunk/lib/Support/Threading.cpp Thu Jun 19 13:18:23 2014
>>>>> @@ -7,7 +7,8 @@
>>>>> //
>>>>>
>>>>> //===----------------------------------------------------------------------===//
>>>>> //
>>>>> -// This file implements llvm_start_multithreaded() and friends.
>>>>> +// This file defines helper functions for running LLVM in a
>>>>> multi-threaded
>>>>> +// environment.
>>>>> //
>>>>>
>>>>> //===----------------------------------------------------------------------===//
>>>>>
>>>>> @@ -19,38 +20,14 @@
>>>>>
>>>>> using namespace llvm;
>>>>>
>>>>> -static bool multithreaded_mode = false;
>>>>> -
>>>>> -bool llvm::llvm_start_multithreaded() {
>>>>> +bool llvm::llvm_is_multithreaded() {
>>>>> #if LLVM_ENABLE_THREADS != 0
>>>>> - assert(!multithreaded_mode && "Already multithreaded!");
>>>>> - multithreaded_mode = true;
>>>>> -
>>>>> - // We fence here to ensure that all initialization is complete
>>>>> BEFORE we
>>>>> - // return from llvm_start_multithreaded().
>>>>> - sys::MemoryFence();
>>>>> return true;
>>>>> #else
>>>>> return false;
>>>>> #endif
>>>>> }
>>>>>
>>>>> -void llvm::llvm_stop_multithreaded() {
>>>>> -#if LLVM_ENABLE_THREADS != 0
>>>>> - assert(multithreaded_mode && "Not currently multithreaded!");
>>>>> -
>>>>> - // We fence here to insure that all threaded operations are
>>>>> complete BEFORE we
>>>>> - // return from llvm_stop_multithreaded().
>>>>> - sys::MemoryFence();
>>>>> -
>>>>> - multithreaded_mode = false;
>>>>> -#endif
>>>>> -}
>>>>> -
>>>>> -bool llvm::llvm_is_multithreaded() {
>>>>> - return multithreaded_mode;
>>>>> -}
>>>>> -
>>>>> #if LLVM_ENABLE_THREADS != 0 && defined(HAVE_PTHREAD_H)
>>>>> #include <pthread.h>
>>>>>
>>>>>
>>>>> Modified: llvm/trunk/unittests/Support/ManagedStatic.cpp
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/ManagedStatic.cpp?rev=211287&r1=211286&r2=211287&view=diff
>>>>>
>>>>> ==============================================================================
>>>>> --- llvm/trunk/unittests/Support/ManagedStatic.cpp (original)
>>>>> +++ llvm/trunk/unittests/Support/ManagedStatic.cpp Thu Jun 19 13:18:23
>>>>> 2014
>>>>> @@ -47,7 +47,6 @@ TEST(Initialize, MultipleThreads) {
>>>>> void *p1 = test1::allocate_stack(a1);
>>>>> void *p2 = test1::allocate_stack(a2);
>>>>>
>>>>> - llvm_start_multithreaded();
>>>>> pthread_t t1, t2;
>>>>> pthread_create(&t1, &a1, test1::helper, nullptr);
>>>>> pthread_create(&t2, &a2, test1::helper, nullptr);
>>>>> @@ -55,7 +54,6 @@ TEST(Initialize, MultipleThreads) {
>>>>> pthread_join(t2, nullptr);
>>>>> free(p1);
>>>>> free(p2);
>>>>> - llvm_stop_multithreaded();
>>>>> }
>>>>> #endif
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> llvm-commits mailing list
>>>>> llvm-commits at cs.uiuc.edu
>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>>>>
>>>>
>>>>
>>>
>>
>
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