src/global.h


Log

Author Commit Date CI Message
Patrick Steinhardt 5c6180b5 2019-11-29T11:06:11 global: convert to fiber-local storage to fix exit races On Windows platforms, we automatically clean up the thread-local storage upon detaching a thread via `DllMain()`. The thing is that this happens for every thread of applications that link against the libgit2 DLL, even those that don't have anything to do with libgit2 itself. As a result, we cannot assume that these unsuspecting threads make use of our `git_libgit2_init()` and `git_libgit2_shutdow()` reference counting, which may lead to racy situations: Thread 1 Thread 2 git_libgit2_shutdown() DllMain(DETACH_THREAD) git__free_tls_data() git_atomic_dec() == 0 git__free_tls_data() TlsFree(_tls_index) TlsGetValue(_tls_index) Due to the second thread never having executed `git_libgit2_init()`, the first thread will clean up TLS data and as a result also free the `_tls_index` variable. When detaching the second thread, we unconditionally access the now-free'd `_tls_index` variable, which is obviously not going to work out well. Fix the issue by converting the code to use fiber-local storage instead of thread-local storage. While FLS will behave the exact same as TLS if no fibers are in use, it does allow us to specify a destructor similar to the one that is accepted by pthread_key_create(3P). Like this, we do not have to manually free indices anymore, but will let the FLS handle calling the destructor. This allows us to get rid of `DllMain()` completely, as we only used it to keep track of when threads were exiting and results in an overall simplification of TLS cleanup.
Etienne Samson 22317057 2017-03-21T00:36:32 https: Prevent OpenSSL from namespace-leaking
Patrick Steinhardt 0c7f49dd 2017-06-30T13:39:01 Make sure to always include "common.h" first Next to including several files, our "common.h" header also declares various macros which are then used throughout the project. As such, we have to make sure to always include this file first in all implementation files. Otherwise, we might encounter problems or even silent behavioural differences due to macros or defines not being defined as they should be. So in fact, our header and implementation files should make sure to always include "common.h" first. This commit does so by establishing a common include pattern. Header files inside of "src" will now always include "common.h" as its first other file, separated by a newline from all the other includes to make it stand out as special. There are two cases for the implementation files. If they do have a matching header file, they will always include this one first, leading to "common.h" being transitively included as first file. If they do not have a matching header file, they instead include "common.h" as first file themselves. This fixes the outlined problems and will become our standard practice for header and source files inside of the "src/" from now on.
Edward Thomson 82f15896 2016-11-18T07:19:22 threads: introduce `git_thread_exit` Introduce `git_thread_exit`, which will allow threads to terminate at an arbitrary time, returning a `void *`. On Windows, this means that we need to store the current `git_thread` in TLS, so that we can set its `return` value when terminating. We cannot simply use `ExitThread`, since Win32 returns `DWORD`s from threads; we return `void *`.
Dirkjan Bussink fa72d6da 2016-03-14T12:02:00 Setup better defaults for OpenSSL ciphers This ensures that when using OpenSSL a safe default set of ciphers is selected. This is done so that the client communicates securely and we don't accidentally enable unsafe ciphers like RC4, or even worse some old export ciphers. Implements the first part of https://github.com/libgit2/libgit2/issues/3682
Carlos Martín Nieto de870533 2015-10-02T03:43:11 settings: add a setter for a custom user-agent
Carlos Martín Nieto f85fc367 2015-07-26T21:12:00 error: store the error messages in a reusable buffer Instead of allocating a brand new buffer for each error string we want to store, we can use a per-thread buffer to store the error string and re-use the underlying storage. We already use the buffer to format the string, so this mostly makes that more direct.
Carlos Martín Nieto 24e53d2f 2015-03-19T09:55:20 Rename GIT_SSL to GIT_OPENSSL This is what it's meant all along, but now we actually have multiple implementations, it's clearer to use the name of the library.
Jeff Hostetler 06c985d8 2015-04-18T09:07:48 Rename routine to free TLS data
Jeff Hostetler 55c5f756 2015-04-17T09:30:22 Attempt to fix Windows TLS memory leak.
Ciro Santilli 3b2cb2c9 2014-09-16T11:49:25 Factor 40 and 41 constants from source.
Vicent Marti 4ca0b566 2014-08-18T12:41:06 oid: Export `git_oid_tostr_s` instead of `_allocfmt` The old `allocfmt` is of no use to callers, as they are not able to free the returned buffer. Export a new API that returns a static string that doesn't need to be freed.
Carlos Martín Nieto 081e76ba 2014-06-12T16:20:52 ssl: init everything all the time Bring together all of the OpenSSL initialization to git_threads_init() so it's together and doesn't need locks. Moving it here also gives us libssh2 thread safety (when built against openssl).
Carlos Martín Nieto cf15ac8a 2014-06-12T03:20:34 ssl: cargo-cult thread safety OpenSSL's tests init everything in the main thread, so let's do that.
Carlos Martín Nieto 1d3364ac 2014-06-11T20:52:15 netops: init OpenSSL once under lock The OpenSSL init functions are not reentrant, which means that running multiple fetches in parallel can cause us to crash. Use a mutex to init OpenSSL, and since we're adding this extra checks, init it only once.
Russell Belfer a3aa5f4d 2013-09-11T12:45:20 Add simple global shutdown hooks Increasingly there are a number of components that want to do some cleanup at global shutdown time (at least if there are not going to be memory leaks). This creates a very simple system of shutdown hooks that will be invoked by git_threads_shutdown. Right now, the maximum number of hooks is hardcoded, but since adding a hook is not a public API, it should be fine and I thought it was better to start off with really simple code.
Russell Belfer e976b56d 2013-04-15T14:27:53 Add git__compare_and_swap and use it This removes the lock from the repository object and changes the internals to use the new atomic git__compare_and_swap to update the _odb, _config, _index, and _refdb variables in a threadsafe manner.
Edward Thomson 359fc2d2 2013-01-08T17:07:25 update copyrights
Edward Thomson a8527429 2012-11-13T14:48:10 unload dll / destroy hash ctxs at shutdown
Edward Thomson 7ebefd22 2012-11-13T10:10:40 move hash library func ptrs to global global
Edward Thomson d6fb0924 2012-11-05T12:37:15 Win32 CryptoAPI and CNG support for SHA1
Carlos Martín Nieto 8cef828d 2012-08-18T22:11:49 Make the memory-window conrol structures global Up to now, the idea was that the user would do all the operations for one repository in the same thread. Thus we could have the memory-mapped window information thread-local and avoid any locking. This is not practical in a few environments, such as Apple's GCD which allocates threads arbitrarily or the .NET CLR, where the OS-level thread can change at any moment. Make the control structure global and protect it with a mutex so we don't depend on the thread currently executing the code.
Michael Schubert 6fc0bdc5 2012-07-17T10:52:16 Remove old error handling code
Vicent Martí 1a481123 2012-02-17T00:13:34 error-handling: References Yes, this is error handling solely for `refs.c`, but some of the abstractions leak all ofer the code base.
schu 5e0de328 2012-02-13T17:10:24 Update Copyright header Signed-off-by: schu <schu-github@schulog.org>
Vicent Marti a15c550d 2011-11-16T14:09:44 threads: Fix the shared global state with TLS See `global.c` for a description of what we're doing. When libgit2 is built with GIT_THREADS support, the threading system must be explicitly initialized with `git_threads_init()`.