kmx git

Commit	Date	Message
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.
22317057	2017-03-21T00:36:32	https: Prevent OpenSSL from namespace-leaking
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.
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 `.
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
de870533	2015-10-02T03:43:11	settings: add a setter for a custom user-agent
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.
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.
06c985d8	2015-04-18T09:07:48	Rename routine to free TLS data
55c5f756	2015-04-17T09:30:22	Attempt to fix Windows TLS memory leak.
3b2cb2c9	2014-09-16T11:49:25	Factor 40 and 41 constants from source.
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.
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).
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.
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.
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.
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.
359fc2d2	2013-01-08T17:07:25	update copyrights
a8527429	2012-11-13T14:48:10	unload dll / destroy hash ctxs at shutdown
7ebefd22	2012-11-13T10:10:40	move hash library func ptrs to global global
d6fb0924	2012-11-05T12:37:15	Win32 CryptoAPI and CNG support for SHA1
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.
6fc0bdc5	2012-07-17T10:52:16	Remove old error handling code
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.
5e0de328	2012-02-13T17:10:24	Update Copyright header Signed-off-by: schu <schu-github@schulog.org>
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()`.

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.

22317057

2017-03-21T00:36:32

https: Prevent OpenSSL from namespace-leaking

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.

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 *`.

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

de870533

2015-10-02T03:43:11

settings: add a setter for a custom user-agent

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.

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.

06c985d8

2015-04-18T09:07:48

Rename routine to free TLS data

55c5f756

2015-04-17T09:30:22

Attempt to fix Windows TLS memory leak.

3b2cb2c9

2014-09-16T11:49:25

Factor 40 and 41 constants from source.

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.

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).

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.

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.

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.

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.

359fc2d2

2013-01-08T17:07:25

update copyrights

a8527429

2012-11-13T14:48:10

unload dll / destroy hash ctxs at shutdown

7ebefd22

2012-11-13T10:10:40

move hash library func ptrs to global global

d6fb0924

2012-11-05T12:37:15

Win32 CryptoAPI and CNG support for SHA1

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.

6fc0bdc5

2012-07-17T10:52:16

Remove old error handling code

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.

5e0de328

2012-02-13T17:10:24

Update Copyright header Signed-off-by: schu <schu-github@schulog.org>

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()`.

thodg/libgit2/src/global.h

src/global.h

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