[llvm] r211900 - Re-apply r211287: Remove support for LLVM runtime multi-threading.
Chandler Carruth
chandlerc at gmail.com
Tue Nov 18 14:17:44 PST 2014
I tried to solve it and failed. =[ It is deeply, fundamentally intertwined
with the existing pass manager.
We solved some of the most egregious cases. The current problems I'm aware
of only impact the cost of creating and tearing down a pass manager, or
running passes with asserts enabled. I only see this show up as a real
problem when running the regression test suite...
Do you have some specific use case that is continuing to cause you problems.
On Tue, Nov 18, 2014 at 1:12 PM, Bruno Cardoso Lopes <
bruno.cardoso at gmail.com> wrote:
> Ping :-)
>
> On Tue, Sep 30, 2014 at 8:13 PM, Bruno Cardoso Lopes <
> bruno.cardoso at gmail.com> wrote:
>
>> Hi Chandler,
>>
>> IIRC, you're working on a fix for the compile time regression caused
>> by this commit. Gently ping :-)
>> Any news on a that or any ideas you may share on how to solve it?
>>
>> Thanks again,
>>
>> Reference: http://llvm.org/bugs/show_bug.cgi?id=20641
>>
>> On Fri, Jun 27, 2014 at 12:13 PM, Chandler Carruth <chandlerc at gmail.com>
>> wrote:
>> > Author: chandlerc
>> > Date: Fri Jun 27 10:13:01 2014
>> > New Revision: 211900
>> >
>> > URL: http://llvm.org/viewvc/llvm-project?rev=211900&view=rev
>> > Log:
>> > Re-apply r211287: Remove support for LLVM runtime multi-threading.
>> >
>> > I'll fix the problems in libclang and other projects in ways that don't
>> > require <mutex> until we sort out the cygwin situation.
>> >
>> > 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=211900&r1=211899&r2=211900&view=diff
>> >
>> ==============================================================================
>> > --- llvm/trunk/docs/ProgrammersManual.rst (original)
>> > +++ llvm/trunk/docs/ProgrammersManual.rst Fri Jun 27 10:13:01 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=211900&r1=211899&r2=211900&view=diff
>> >
>> ==============================================================================
>> > --- llvm/trunk/include/llvm-c/Core.h (original)
>> > +++ llvm/trunk/include/llvm-c/Core.h Fri Jun 27 10:13:01 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=211900&r1=211899&r2=211900&view=diff
>> >
>> ==============================================================================
>> > --- llvm/trunk/include/llvm/Support/ManagedStatic.h (original)
>> > +++ llvm/trunk/include/llvm/Support/ManagedStatic.h Fri Jun 27 10:13:01
>> 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=211900&r1=211899&r2=211900&view=diff
>> >
>> ==============================================================================
>> > --- llvm/trunk/include/llvm/Support/Threading.h (original)
>> > +++ llvm/trunk/include/llvm/Support/Threading.h Fri Jun 27 10:13:01 2014
>> > @@ -7,7 +7,8 @@
>> > //
>> >
>> //===----------------------------------------------------------------------===//
>> > //
>> > -// TThis file defines llvm_start_multithreaded() and friends.
>> > +// This file declares helper functions for running LLVM in a
>> multi-threaded
>> > +// environment.
>> > //
>> >
>> //===----------------------------------------------------------------------===//
>> >
>> > @@ -15,22 +16,8 @@
>> > #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();
>> > -
>> > - /// llvm_is_multithreaded - Check whether LLVM is executing in
>> thread-safe
>> > - /// mode or not.
>> > + /// 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=211900&r1=211899&r2=211900&view=diff
>> >
>> ==============================================================================
>> > --- llvm/trunk/lib/IR/Core.cpp (original)
>> > +++ llvm/trunk/lib/IR/Core.cpp Fri Jun 27 10:13:01 2014
>> > @@ -2708,11 +2708,10 @@ 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=211900&r1=211899&r2=211900&view=diff
>> >
>> ==============================================================================
>> > --- llvm/trunk/lib/Support/Threading.cpp (original)
>> > +++ llvm/trunk/lib/Support/Threading.cpp Fri Jun 27 10:13:01 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=211900&r1=211899&r2=211900&view=diff
>> >
>> ==============================================================================
>> > --- llvm/trunk/unittests/Support/ManagedStatic.cpp (original)
>> > +++ llvm/trunk/unittests/Support/ManagedStatic.cpp Fri Jun 27 10:13:01
>> 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
>>
>>
>>
>> --
>> Bruno Cardoso Lopes
>> http://www.brunocardoso.cc
>>
>
>
>
> --
> Bruno Cardoso Lopes
> http://www.brunocardoso.cc
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
>
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