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322c15ee
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2020-08-01T18:24:41
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Make the pack and mwindow implementations data-race-free
This change fixes a packfile heap corruption that can happen when
interacting with multiple packfiles concurrently across multiple
threads. This is exacerbated by setting a lower mwindow open file limit.
This change:
* Renames most of the internal methods in pack.c to clearly indicate
that they expect to be called with a certain lock held, making
reasoning about the state of locks a bit easier.
* Splits the `git_pack_file` lock in two: the one in `git_pack_file`
only protects the `index_map`. The protection to `git_mwindow_file` is
now in that struct.
* Explicitly checks for freshness of the `git_pack_file` in
`git_packfile_unpack_header`: this allows the mwindow implementation
to close files whenever there is enough cache pressure, and
`git_packfile_unpack_header` will reopen the packfile if needed.
* After a call to `p_munmap()`, the `data` and `len` fields are poisoned
with `NULL` to make use-after-frees more evident and crash rather than
being open to the possibility of heap corruption.
* Adds a test case to prevent this from regressing in the future.
Fixes: #5591
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e316b0d3
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2020-05-15T11:47:09
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runtime: move init/shutdown into the "runtime"
Provide a mechanism for system components to register for initialization
and shutdown of the libgit2 runtime.
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92d42eb3
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2020-07-12T09:53:10
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Minor nits and style formatting
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d88994da
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2020-06-27T07:34:36
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Create the repository within the test
This change moves the humongous static repository with 1025 commits into
the test file, now with a more modest 16 commits.
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eab2b044
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2020-06-26T16:10:30
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Review feedback
* Change the default of the file limit to 0 (unlimited).
* Changed the heuristic to close files to be the file that contains the
least-recently-used window such that the window is the
most-recently-used in the file, and the file does not have in-use
windows.
* Parameterized the filelimit test to check for a limit of 1 and 100
open windows.
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9679df57
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2020-02-08T20:47:24
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mwindow: set limit on number of open files
There are some cases in which repositories accrue a large number of
packfiles. The existing mwindow limit applies only to the total size of
mmap'd files, not on their number. This leads to a situation in which
having lots of small packfiles could exhaust the allowed number of open
files, particularly on macOS, where the default ulimit is very low
(256).
This change adds a new configuration parameter
(GIT_OPT_SET_MWINDOW_FILE_LIMIT) that sets the maximum number of open
packfiles, with a default of 128. This is low enough so that even macOS
users should not hit it during normal use.
Based on PR #5386, originally written by @josharian.
Fixes: #2758
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