We should be able to reuse this between the implementation of C11 cnd_t
condition variables and POSIX pthread_cond_t condition variables.
The current implementation is hyper linux specific, making use of Futex. That
obviously wont work outside of linux, so split the OS specific functions off
into their own source outside of the header.
Modifies the return values of the to-be-shared impl to return 0 on success and
-1 on error. This pattern was shamelessly stolen from Bionic's
[__bionic_thrd_error](https://android.googlesource.com/platform/bionic/+/refs/heads/main/libc/include/bits/threads_inlines.h#41).
Fixes: #88580
Link: #88583
This PR address issue #89002.
#### Changes in this PR
* Added a simple implementation of `cpp::lock_guard` (an equivalent of
`std::lock_guard`) in libc/src/__support/CPP inspired by the libstdc++
implementation
* Added tests for `cpp::lock_guard` in
/libc/test/src/__support/CPP/mutex_test.cpp
* Replaced all references to `MutexLock` with `cpp::lock_guard`
---------
Co-authored-by: Guillaume Chatelet <gchatelet@google.com>
# Motivation
Futex syscalls are widely used in our codebase as synchronization
mechanism. Hence, it may be worthy to abstract out the most common
routines (wait and wake). On the other hand, C++20 also provides
`std::atomic_notify_one/std::atomic_wait/std::atomic_notify_all` which
align with such functionalities. This PR introduces `Futex` as a subtype
of `cpp::Atomic<FutexWordType>` with additional
`notify_one/notify_all/wait` operations.
Providing such wrappers also make future porting easier. For example,
FreeBSD's `_umtx_op` and Darwin's `ulock` can be wrapped in a similar
manner.
### Similar Examples
1. [bionic
futex](https://android.googlesource.com/platform/bionic/+/refs/heads/main/libc/bionic/bionic_futex.cpp)
2. [futex in Rust's
std](8cef37dbb6/library/std/src/sys/pal/unix/futex.rs (L21))
This patch is large, but is almost entirely just adding casts to calls
to syscall_impl. Much of the work was done programatically, with human
checking when the syntax or types got confusing.
Reviewed By: mcgrathr
Differential Revision: https://reviews.llvm.org/D156950
This patch adds a bunch of ifdefs to handle the 32 bit versions of
some syscalls, which often only append a 64 to the name of the syscall
(with exception of SYS_lseek -> SYS_llseek and SYS_futex ->
SYS_futex_time64)
This patch also tries to handle cases where wait4 is not available
(as in riscv32): to implement wait, wait4 and waitpid when wait4 is
not available, we check for alternative wait calls and ultimately rely
on waitid to implement them all.
In riscv32, only waitid is available, so we need it to support this
platform.
Reviewed By: michaelrj
Differential Revision: https://reviews.llvm.org/D148371
Only functional for stack growsdown (same as before), but custom
`stack`, `stacksize`, `guardsize`, and `detachstate` all should be
working.
Differential Revision: https://reviews.llvm.org/D148290
Add the syscall wrapper function and tests. It's implemented using a
macro to guarantee the minimum number of arguments.
Reviewed By: sivachandra, lntue
Differential Revision: https://reviews.llvm.org/D134919
The existing thrd_once function has been refactored so that the
implementation can be shared between thrd_once and pthread_once
functions.
Reviewed By: michaelrj
Differential Revision: https://reviews.llvm.org/D134716
Specifically, POSIX functions pthread_key_create, pthread_key_delete,
pthread_setspecific and pthread_getspecific have been added. The C
standard equivalents tss_create, tss_delete, tss_set and tss_get have
also been added.
Reviewed By: lntue, michaelrj
Differential Revision: https://reviews.llvm.org/D131647
Tests for pthread_detach and thrd_detach have not been added. Instead, a
test for the underlying implementation has been added as it makes use of
an internal wait method to synchronize with detached threads.
Reviewed By: lntue, michaelrj
Differential Revision: https://reviews.llvm.org/D127479
The state is now stored on the thread's stack memory. This enables
implementing pthread API like pthread_detach which takes the pthread_t
structure argument by value.
Reviewed By: lntue
Differential Revision: https://reviews.llvm.org/D126716
This change is essentially a mechanical change which moves the thread
creation and join implementations from src/threads/linux to
src/__support/threads/linux/thread.h. The idea being that, in future, a
pthread implementation can reuse the common thread implementations in
src/__support/threads.
Reviewed By: lntue
Differential Revision: https://reviews.llvm.org/D123287
Instead, memory is allocated and deallocated using mmap and munmap
syscalls directly.
Reviewed By: lntue, michaelrj
Differential Revision: https://reviews.llvm.org/D122876
The platform independent file implementation is not an entrypoint so it
cannot be excluded via the entrypoints.txt file. Hence, we need a
special treatment to exclude it from the build.
Reviewed By: michaelrj
Differential Revision: https://reviews.llvm.org/D121947
The idea is that, other parts of the libc which require thread/lock
support will be able to use this platform independent setup.
With this change, only the linux implementation of a mutex type has been
moved to the new library. Because of this, there is some duplication
between the new library and src/threads/linux. A follow up change will
move all of src/threads/linux to the new library. The duplication should
be eliminated with that move.
Reviewed By: lntue
Differential Revision: https://reviews.llvm.org/D120795
With modern architectures having a thread pointer and language supporting
thread locals, there is no reason to use a function intermediary to access
the thread local errno value.
The entrypoint corresponding to errno has been replaced with an object
library as there is no formal entrypoint for errno anymore.
Reviewed By: jeffbailey, michaelrj
Differential Revision: https://reviews.llvm.org/D120920
New methods to the Atomic class have been added as required. Futex
related types have been consolidated at a common place.
Reviewed By: lntue
Differential Revision: https://reviews.llvm.org/D120705
Only the methods currently required by the libc have been added.
Most of the existing uses of atomic operations have been switched over
to this new class. A future change will clean up the rest of uses.
This change now allows building mutex and condition variable code with a
C++ compiler which does not have stdatomic.h, for example g++.
Reviewed By: lntue
Differential Revision: https://reviews.llvm.org/D120642
This patch applies the lint rules described in the previous patch. There
was also a significant amount of effort put into manually fixing things,
since all of the templated functions, or structs defined in /spec, were
not updated and had to be handled manually.
Reviewed By: sivachandra, lntue
Differential Revision: https://reviews.llvm.org/D114302
This patch adds a skeleton as a preparatory step for the next patch which
adds the actual implementations of the condition variable functions.
Reviewed By: michaelrj
Differential Revision: https://reviews.llvm.org/D108947
This allows others parts of the libc to use the mutex types without
actually pulling in public function implementations.
Along the way, few cleanups have been done, like using a uniform type to
refer the linux futex word.
Reviewed By: michaelrj
Differential Revision: https://reviews.llvm.org/D108749
Current implementation defines LIBC_TARGET_MACHINE with the use of CMAKE_SYSTEM_PROCESSOR.
Unfortunately CMAKE_SYSTEM_PROCESSOR is OS dependent and can produce different results.
An evidence of this is the various matchers used to detect whether the architecture is x86.
This patch normalizes LIBC_TARGET_MACHINE and renames it LIBC_TARGET_ARCHITECTURE.
I've added many architectures but we may want to limit ourselves to x86 and ARM.
Differential Revision: https://reviews.llvm.org/D101524
this will make sure that all of the functions are using the correct
prototypes. Explained much better in the comments of this diff:
https://reviews.llvm.org/D94195
Summary:
The new macro also inserts the C alias for the C++ implementations
without needing an objcopy based post processing step. The CMake
rules have been updated to reflect this. More CMake cleanup can be
taken up in future rounds and appropriate TODOs have been added for them.
Reviewers: mcgrathr, sivachandra
Subscribers:
