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In Git 2.36 we revamped the way how hooks are invoked. One change
that is end-user visible is that the output of a hook is no longer
directly connected to the standard output of "git" that spawns the
hook, which was noticed post release. This is getting corrected.
* ab/hooks-regression-fix:
hook API: fix v2.36.0 regression: hooks should be connected to a TTY
run-command: add an "ungroup" option to run_process_parallel()
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Rename .env_array member to .env in the child_process structure.
* ab/env-array:
run-command API users: use "env" not "env_array" in comments & names
run-command API: rename "env_array" to "env"
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Extend the parallel execution API added in c553c72eed6 (run-command:
add an asynchronous parallel child processor, 2015-12-15) to support a
mode where the stdout and stderr of the processes isn't captured and
output in a deterministic order, instead we'll leave it to the kernel
and stdio to sort it out.
This gives the API same functionality as GNU parallel's --ungroup
option. As we'll see in a subsequent commit the main reason to want
this is to support stdout and stderr being connected to the TTY in the
case of jobs=1, demonstrated here with GNU parallel:
$ parallel --ungroup 'test -t {} && echo TTY || echo NTTY' ::: 1 2
TTY
TTY
$ parallel 'test -t {} && echo TTY || echo NTTY' ::: 1 2
NTTY
NTTY
Another is as GNU parallel's documentation notes a potential for
optimization. As demonstrated in next commit our results with "git
hook run" will be similar, but generally speaking this shows that if
you want to run processes in parallel where the exact order isn't
important this can be a lot faster:
$ hyperfine -r 3 -L o ,--ungroup 'parallel {o} seq ::: 10000000 >/dev/null '
Benchmark 1: parallel seq ::: 10000000 >/dev/null
Time (mean ± σ): 220.2 ms ± 9.3 ms [User: 124.9 ms, System: 96.1 ms]
Range (min … max): 212.3 ms … 230.5 ms 3 runs
Benchmark 2: parallel --ungroup seq ::: 10000000 >/dev/null
Time (mean ± σ): 154.7 ms ± 0.9 ms [User: 136.2 ms, System: 25.1 ms]
Range (min … max): 153.9 ms … 155.7 ms 3 runs
Summary
'parallel --ungroup seq ::: 10000000 >/dev/null ' ran
1.42 ± 0.06 times faster than 'parallel seq ::: 10000000 >/dev/null '
A large part of the juggling in the API is to make the API safer for
its maintenance and consumers alike.
For the maintenance of the API we e.g. avoid malloc()-ing the
"pp->pfd", ensuring that SANITIZE=address and other similar tools will
catch any unexpected misuse.
For API consumers we take pains to never pass the non-NULL "out"
buffer to an API user that provided the "ungroup" option. The
resulting code in t/helper/test-run-command.c isn't typical of such a
user, i.e. they'd typically use one mode or the other, and would know
whether they'd provided "ungroup" or not.
We could also avoid the strbuf_init() for "buffered_output" by having
"struct parallel_processes" use a static PARALLEL_PROCESSES_INIT
initializer, but let's leave that cleanup for later.
Using a global "run_processes_parallel_ungroup" variable to enable
this option is rather nasty, but is being done here to produce as
minimal of a change as possible for a subsequent regression fix. This
change is extracted from a larger initial version[1] which ends up
with a better end-state for the API, but in doing so needed to modify
all existing callers of the API. Let's defer that for now, and
narrowly focus on what we need for fixing the regression in the
subsequent commit.
It's safe to do this with a global variable because:
A) hook.c is the only user of it that sets it to non-zero, and before
we'll get any other API users we'll refactor away this method of
passing in the option, i.e. re-roll [1].
B) Even if hook.c wasn't the only user we don't have callers of this
API that concurrently invoke this parallel process starting API
itself in parallel.
As noted above "A" && "B" are rather nasty, and we don't want to live
with those caveats long-term, but for now they should be an acceptable
compromise.
1. https://lore.kernel.org/git/cover-v2-0.8-00000000000-20220518T195858Z-avarab@gmail.com/
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Follow-up on a preceding commit which changed all references to the
"env_array" when referring to the "struct child_process" member. These
changes are all unnecessary for the compiler, but help the code's
human readers.
All the comments that referred to "env_array" have now been updated,
as well as function names and variables that had "env_array" in their
name, they now refer to "env".
In addition the "out" name for the submodule.h prototype was
inconsistent with the function definition's use of "env_array" in
submodule.c. Both of them use "env" now.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Start following-up on the rename mentioned in c7c4bdeccf3 (run-command
API: remove "env" member, always use "env_array", 2021-11-25) of
"env_array" to "env".
The "env_array" name was picked in 19a583dc39e (run-command: add
env_array, an optional argv_array for env, 2014-10-19) because "env"
was taken. Let's not forever keep the oddity of "*_array" for this
"struct strvec", but not for its "args" sibling.
This commit is almost entirely made with a coccinelle rule[1]. The
only manual change here is in run-command.h to rename the struct
member itself and to change "env_array" to "env" in the
CHILD_PROCESS_INIT initializer.
The rest of this is all a result of applying [1]:
* make contrib/coccinelle/run_command.cocci.patch
* patch -p1 <contrib/coccinelle/run_command.cocci.patch
* git add -u
1. cat contrib/coccinelle/run_command.pending.cocci
@@
struct child_process E;
@@
- E.env_array
+ E.env
@@
struct child_process *E;
@@
- E->env_array
+ E->env
I've avoided changing any comments and derived variable names here,
that will all be done in the next commit.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Remove a "struct child_process" member added in
ac2fbaa674c (run-command: add clean_on_exit_handler, 2016-10-16), but
which was never used.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The new hook.h library has replaced all run-command.h hook-related
functionality. So let's delete this dead code.
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Acked-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Move the post-index-change hook away from run-command.h to and over to
the new hook.h library.
This removes the last direct user of "run_hook_ve()" outside of
run-command.c ("run_hook_le()" still uses it). So we can make the
function static now. A subsequent commit will remove this code
entirely when "run_hook_le()" itself goes away.
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Acked-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Remove the "env" member from "struct child_process" in favor of always
using the "env_array". As with the preceding removal of "argv" in
favor of "args" this gets rid of current and future oddities around
memory management at the API boundary (see the amended API docs).
For some of the conversions we can replace patterns like:
child.env = env->v;
With:
strvec_pushv(&child.env_array, env->v);
But for others we need to guard the strvec_pushv() with a NULL check,
since we're not passing in the "v" member of a "struct strvec",
e.g. in the case of tmp_objdir_env()'s return value.
Ideally we'd rename the "env_array" member to simply "env" as a
follow-up, since it and "args" are now inconsistent in not having an
"_array" suffix, and seemingly without any good reason, unless we look
at the history of how they came to be.
But as we've currently got 122 in-tree hits for a "git grep env_array"
let's leave that for now (and possibly forever). Doing that rename
would be too disruptive.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Remove the "argv" member from the run-command API, ever since "args"
was added in c460c0ecdca (run-command: store an optional argv_array,
2014-05-15) being able to provide either "argv" or "args" has led to
some confusion and bugs.
If we hadn't gone in that direction and only had an "argv" our
problems wouldn't have been solved either, as noted in [1] (and in the
documentation amended here) it comes with inherent memory management
issues: The caller would have to hang on to the "argv" until the
run-command API was finished. If the "argv" was an argument to main()
this wasn't an issue, but if it it was manually constructed using the
API might be painful.
We also have a recent report[2] of a user of the API segfaulting,
which is a direct result of it being complex to use. This commit
addresses the root cause of that bug.
This change is larger than I'd like, but there's no easy way to avoid
it that wouldn't involve even more verbose intermediate steps. We use
the "argv" as the source of truth over the "args", so we need to
change all parts of run-command.[ch] itself, as well as the trace2
logging at the same time.
The resulting Windows-specific code in start_command() is a bit nasty,
as we're now assigning to a strvec's "v" member, instead of to our own
"argv". There was a suggestion of some alternate approaches in reply
to an earlier version of this commit[3], but let's leave larger a
larger and needless refactoring of this code for now.
1. http://lore.kernel.org/git/YT6BnnXeAWn8BycF@coredump.intra.peff.net
2. https://lore.kernel.org/git/20211120194048.12125-1-ematsumiya@suse.de/
3. https://lore.kernel.org/git/patch-5.5-ea1011f7473-20211122T153605Z-avarab@gmail.com/
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Built-in fsmonitor (part 1).
* jh/builtin-fsmonitor-part1:
t/helper/simple-ipc: convert test-simple-ipc to use start_bg_command
run-command: create start_bg_command
simple-ipc/ipc-win32: add Windows ACL to named pipe
simple-ipc/ipc-win32: add trace2 debugging
simple-ipc: move definition of ipc_active_state outside of ifdef
simple-ipc: preparations for supporting binary messages.
trace2: add trace2_child_ready() to report on background children
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Move the find_hook() function from run-command.c to a new hook.c
library. This change establishes a stub library that's pretty
pointless right now, but will see much wider use with Emily Shaffer's
upcoming "configuration-based hooks" series.
Eventually all the hook related code will live in hook.[ch]. Let's
start that process by moving the simple find_hook() function over
as-is.
Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Rewrite of "git bisect" in C continues.
* mr/bisect-in-c-4:
bisect--helper: retire `--bisect-next-check` subcommand
bisect--helper: reimplement `bisect_run` shell function in C
bisect--helper: reimplement `bisect_visualize()` shell function in C
run-command: make `exists_in_PATH()` non-static
t6030-bisect-porcelain: add test for bisect visualize
t6030-bisect-porcelain: add tests to control bisect run exit cases
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Create a variation of `run_command()` and `start_command()` to launch a command
into the background and optionally wait for it to become "ready" before returning.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Remove the `static` keyword from `exists_in_PATH()` function
and declare the function in `run-command.h` file.
The function will be used in bisect_visualize() in a later
commit.
Mentored by: Christian Couder <chriscool@tuxfamily.org>
Mentored by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Tanushree Tumane <tanushreetumane@gmail.com>
Signed-off-by: Miriam Rubio <mirucam@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Especially on Windows, where files cannot be deleted if _any_ process
holds an open file handle to them, it is important to close the object
store (releasing all handles to all `.pack` files) before running a
command that might spawn a garbage collection.
This scenario is so common that we frequently see the pattern of closing
the object store before running auto maintenance or another Git command.
Let's make this much more convenient by teaching the `run_command()`
machinery a new flag to release the object store before spawning the
process.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The values were listed unaligned, and with powers of two spelled out in
decimal. The list is easier to parse for human readers if the numbers
are aligned and spelled out as powers of two (using the bit-shift
operator `<<`).
While at it, remove a code comment that was unclear at best, and
confusing at worst.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Prepare the internals for lazily fetching objects in submodules
from their promisor remotes.
* jt/partial-clone-submodule-1:
promisor-remote: teach lazy-fetch in any repo
run-command: refactor subprocess env preparation
submodule: refrain from filtering GIT_CONFIG_COUNT
promisor-remote: support per-repository config
repository: move global r_f_p_c to repo struct
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Move *_INIT macros I'll use in a subsequent commits to designated
initializers. This isn't required for those follow-up changes, but
since next commits will change things in this area, let's use the
modern pattern over the old one while we're at it.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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submodule.c has functionality that prepares the environment for running
a subprocess in a new repo. The lazy-fetching code (used in partial
clones) will need this in a subsequent commit, so move it to a more
central location.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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It's unclear how run-command's use_shell option should impact the
arguments fed to a command. Plausibly it could mean that we glue all of
the arguments together into a string to pass to the shell, in which case
that opens the question of whether the caller needs to quote them.
But in fact we don't implement it that way (and even if we did, we'd
probably auto-quote the arguments as part of the glue step). And we must
not receive quoted arguments, because we might actually optimize out the
shell entirely (i.e., the caller does not even know if a shell will be
involved in the end or not).
Since this ambiguity may have been the cause of a recent bug, let's
document the option a bit.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The run_auto_gc() method is used in several places to trigger a check
for repo maintenance after some Git commands, such as 'git commit' or
'git fetch'.
To allow for extra customization of this maintenance activity, replace
the 'git gc --auto [--quiet]' call with one to 'git maintenance run
--auto [--quiet]'. As we extend the maintenance builtin with other
steps, users will be able to select different maintenance activities.
Rename run_auto_gc() to run_auto_maintenance() to be clearer what is
happening on this call, and to expose all callers in the current diff.
Rewrite the method to use a struct child_process to simplify the calls
slightly.
Since 'git fetch' already allows disabling the 'git gc --auto'
subprocess, add an equivalent option with a different name to be more
descriptive of the new behavior: '--[no-]maintenance'. Update the
documentation to include these options at the same time.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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We eventually want to drop the argv_array name and just use strvec
consistently. There's no particular reason we have to do it all at once,
or care about interactions between converted and unconverted bits.
Because of our preprocessor compat layer, the names are interchangeable
to the compiler (so even a definition and declaration using different
names is OK).
This patch converts all of the remaining files, as the resulting diff is
reasonably sized.
The conversion was done purely mechanically with:
git ls-files '*.c' '*.h' |
xargs perl -i -pe '
s/ARGV_ARRAY/STRVEC/g;
s/argv_array/strvec/g;
'
We'll deal with any indentation/style fallouts separately.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This requires updating #include lines across the code-base, but that's
all fairly mechanical, and was done with:
git ls-files '*.c' '*.h' |
xargs perl -i -pe 's/argv-array.h/strvec.h/'
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When an aliased command, whose output is piped to a pager by git,
gets killed by a signal, the pager got into a funny state, which
has been corrected (again).
* ta/wait-on-aliased-commands-upon-signal:
Wait for child on signal death for aliases to externals
Wait for child on signal death for aliases to builtins
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When you hit ^C all the processes in the tree receives it. When a git
command uses a pager, git ignores this and waits until the pager quits.
However, when using an alias there is an additional process in the tree
which didn't ignore the signal. That caused it to exit which in turn
caused the pager to exit. This fixes that for aliases to builtins.
This was originally fixed in 46df6906 (execv_dashed_external: wait
for child on signal death, 2017-01-06), but was broken by ee4512ed
(trace2: create new combined trace facility, 2019-02-22) and then
b9140840 (git: avoid calling aliased builtins via their dashed form,
2019-07-29).
Signed-off-by: Trygve Aaberge <trygveaa@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Back in 1991006c (fetch: convert argv_gc_auto to struct argv_array,
2014-08-16), we taught "git fetch --quiet" to pass the "--quiet"
option down to "gc --auto". This issue, however, is not limited to
"fetch":
$ git grep -e 'gc.*--auto' \*.c
finds hits in "am", "commit", "merge", and "rebase" and these
commands do not pass "--quiet" down to "gc --auto" when they
themselves are told to be quiet.
As a preparatory step, let's introduce a helper function
run_auto_gc(), that the caller can pass a boolean "quiet",
and redo the fix to "git fetch" using the helper.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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An accidental conversion of a tab to 4 spaces snuck into 4c4066d95d
(run-command: move doc to run-command.h, 2019-11-17), messing up the
alignment when you have the project-recommended 8-width tabstops. Let's
revert that line.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Move the documentation from Documentation/technical/api-run-command.txt
to run-command.h as it's easier for the developers to find the usage
information beside the code instead of looking for it in another doc file.
Documentation/technical/api-run-command.txt is removed because the
information it has is now redundant and it'll be hard to keep it up to
date and synchronized with the documentation in the header file.
Signed-off-by: Heba Waly <heba.waly@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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There has been a push to remove extern from function declarations.
Finish the job by removing all instances of "extern" for function
declarations in headers using sed.
This was done by running the following on my system with sed 4.2.2:
$ git ls-files \*.{c,h} |
grep -v ^compat/ |
xargs sed -i'' -e 's/^\(\s*\)extern \([^(]*([^*]\)/\1\2/'
Files under `compat/` are intentionally excluded as some are directly
copied from external sources and we should avoid churning them as much
as possible.
Then, leftover instances of extern were found by running
$ git grep -w -C3 extern \*.{c,h}
and manually checking the output. No other instances were found.
Note that the regex used specifically excludes function variables which
_should_ be left as extern.
Not the most elegant way to do it but it gets the job done.
Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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There has been a push to remove extern from function declarations.
Remove some instances of "extern" for function declarations which are
caught by Coccinelle. Note that Coccinelle has some difficulty with
processing functions with `__attribute__` or varargs so some `extern`
declarations are left behind to be dealt with in a future patch.
This was the Coccinelle patch used:
@@
type T;
identifier f;
@@
- extern
T f(...);
and it was run with:
$ git ls-files \*.{c,h} |
grep -v ^compat/ |
xargs spatch --sp-file contrib/coccinelle/noextern.cocci --in-place
Files under `compat/` are intentionally excluded as some are directly
copied from external sources and we should avoid churning them as much
as possible.
Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Create a new unified tracing facility for git. The eventual intent is to
replace the current trace_printf* and trace_performance* routines with a
unified set of git_trace2* routines.
In addition to the usual printf-style API, trace2 provides higer-level
event verbs with fixed-fields allowing structured data to be written.
This makes post-processing and analysis easier for external tools.
Trace2 defines 3 output targets. These are set using the environment
variables "GIT_TR2", "GIT_TR2_PERF", and "GIT_TR2_EVENT". These may be
set to "1" or to an absolute pathname (just like the current GIT_TRACE).
* GIT_TR2 is intended to be a replacement for GIT_TRACE and logs command
summary data.
* GIT_TR2_PERF is intended as a replacement for GIT_TRACE_PERFORMANCE.
It extends the output with columns for the command process, thread,
repo, absolute and relative elapsed times. It reports events for
child process start/stop, thread start/stop, and per-thread function
nesting.
* GIT_TR2_EVENT is a new structured format. It writes event data as a
series of JSON records.
Calls to trace2 functions log to any of the 3 output targets enabled
without the need to call different trace_printf* or trace_performance*
routines.
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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On systems that do not support multithread, start_async() is
implemented with fork(). This implementation details unfortunately
leak out at least in send-pack.c [1].
To keep the code base clean of NO_PTHREADS, move the this #ifdef back
to run-command.c. The new wrapper function async_with_fork() at least
helps suggest that this special "close()" is related to async in fork
mode.
[1] 09c9957cf7 (send-pack: avoid deadlock when pack-object dies early
- 2011-04-25)
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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run-command.c may use threads for its async support. But instead of
including pthread.h directly, let's include thread-utils.h.
run-command.c probably never needs the dummy bits in thread-utils.h
when NO_PTHREADS is defined. But this makes sure we have consistent
HAVE_THREADS behavior everywhere. From now on outside compat/,
thread-utils.h is the only place that includes pthread.h
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Move the logic for 'is_executable()' from help.c to run_command.c and
expose it so that callers from outside help.c can access the function.
This is to enable run-command to be able to query if a file is
executable in a future patch.
Signed-off-by: Brandon Williams <bmwill@google.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When you hit ^C to interrupt a git command going to a pager,
this usually leaves the pager running. But when a dashed
external is in use, the pager ends up in a funny state and
quits (but only after eating one more character from the
terminal!). This fixes it.
Explaining the reason will require a little background.
When git runs a pager, it's important for the git process to
hang around and wait for the pager to finish, even though it
has no more data to feed it. This is because git spawns the
pager as a child, and thus the git process is the session
leader on the terminal. After it dies, the pager will finish
its current read from the terminal (eating the one
character), and then get EIO trying to read again.
When you hit ^C, that sends SIGINT to git and to the pager,
and it's a similar situation. The pager ignores it, but the
git process needs to hang around until the pager is done. We
addressed that long ago in a3da882120 (pager: do
wait_for_pager on signal death, 2009-01-22).
But when you have a dashed external (or an alias pointing to
a builtin, which will re-exec git for the builtin), there's
an extra process in the mix. For instance, running:
$ git -c alias.l=log l
will end up with a process tree like:
git (parent)
\
git-log (child)
\
less (pager)
If you hit ^C, SIGINT goes to all of them. The pager ignores
it, and the child git process will end up in wait_for_pager().
But the parent git process will die, and the usual EIO
trouble happens.
So we really want the parent git process to wait_for_pager(),
but of course it doesn't know anything about the pager at
all, since it was started by the child. However, we can
have it wait on the git-log child, which in turn is waiting
on the pager. And that's what this patch does.
There are a few design decisions here worth explaining:
1. The new feature is attached to run-command's
clean_on_exit feature. Partly this is convenience,
since that feature already has a signal handler that
deals with child cleanup.
But it's also a meaningful connection. The main reason
that dashed externals use clean_on_exit is to bind the
two processes together. If somebody kills the parent
with a signal, we propagate that to the child (in this
instance with SIGINT, we do propagate but it doesn't
matter because the original signal went to the whole
process group). Likewise, we do not want the parent
to go away until the child has done so.
In a traditional Unix world, we'd probably accomplish
this binding by just having the parent execve() the
child directly. But since that doesn't work on Windows,
everything goes through run_command's more spawn-like
interface.
2. We do _not_ automatically waitpid() on any
clean_on_exit children. For dashed externals this makes
sense; we know that the parent is doing nothing but
waiting for the child to exit anyway. But with other
children, it's possible that the child, after getting
the signal, could be waiting on the parent to do
something (like closing a descriptor). If we were to
wait on such a child, we'd end up in a deadlock. So
this errs on the side of caution, and lets callers
enable the feature explicitly.
3. When we send children the cleanup signal, we send all
the signals first, before waiting on any children. This
is to avoid the case where one child might be waiting
on another one to exit, causing a deadlock. We inform
all of them that it's time to die before reaping any.
In practice, there is only ever one dashed external run
from a given process, so this doesn't matter much now.
But it future-proofs us if other callers start using
the wait_after_clean mechanism.
There's no automated test here, because it would end up racy
and unportable. But it's easy to reproduce the situation by
running the log command given above and hitting ^C.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Some processes might want to perform cleanup tasks before Git kills them
due to the 'clean_on_exit' flag. Let's give them an interface for doing
this. The feature is used in a subsequent patch.
Please note, that the cleanup callback is not executed if Git dies of a
signal. The reason is that only "async-signal-safe" functions would be
allowed to be call in that case. Since we cannot control what functions
the callback will use, we will not support the case. See 507d7804 for
more details.
Helped-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Move check_pipe() to run_command and make it public. This is necessary
to call the function from pkt-line in a subsequent patch.
While at it, make async_exit() static to run_command.c as it is no
longer used from outside.
Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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We already have capture_command(), which captures the stdout
of a command in a way that avoids deadlocks. But sometimes
we need to do more I/O, like capturing stderr as well, or
sending data to stdin. It's easy to write code that
deadlocks racily in these situations depending on how fast
the command reads its input, or in which order it writes its
output.
Let's give callers an easy interface for doing this the
right way, similar to what capture_command() did for the
simple case.
The whole thing is backed by a generic poll() loop that can
feed an arbitrary number of buffers to descriptors, and fill
an arbitrary number of strbufs from other descriptors. This
seems like overkill, but the resulting code is actually a
bit cleaner than just handling the three descriptors
(because the output code for stdout/stderr is effectively
duplicated, so being able to loop is a benefit).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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"git push" from a corrupt repository that attempts to push a large
number of refs deadlocked; the thread to relay rejection notices
for these ref updates blocked on writing them to the main thread,
after the main thread at the receiving end notices that the push
failed and decides not to read these notices and return a failure.
* jk/push-client-deadlock-fix:
t5504: drop sigpipe=ok from push tests
fetch-pack: isolate sigpipe in demuxer thread
send-pack: isolate sigpipe in demuxer thread
run-command: teach async threads to ignore SIGPIPE
send-pack: close demux pipe before finishing async process
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Async processes can be implemented as separate forked
processes, or as threads (depending on the NO_PTHREADS
setting). In the latter case, if an async thread gets
SIGPIPE, it takes down the whole process. This is obviously
bad if the main process was not otherwise going to die, but
even if we were going to die, it means the main process does
not have a chance to report a useful error message.
There's also the small matter that forked async processes
will not take the main process down on a signal, meaning git
will behave differently depending on the NO_PTHREADS
setting.
This patch fixes it by adding a new flag to "struct async"
to block SIGPIPE just in the async thread. In theory, this
should always be on (which makes async threads behave more
like async processes), but we would first want to make sure
that each async process we spawn is careful about checking
return codes from write() and would not spew endlessly into
a dead pipe. So let's start with it as optional, and we can
enable it for specific sites in future patches.
The natural name for this option would be "ignore_sigpipe",
since that's what it does for the threaded case. But since
that name might imply that we are ignoring it in all cases
(including the separate-process one), let's call it
"isolate_sigpipe". What we are really asking for is
isolation. I.e., not to have our main process taken down by
signals spawned by the async process. How that is
implemented is up to the run-command code.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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A major part of "git submodule update" has been ported to C to take
advantage of the recently added framework to run download tasks in
parallel.
* sb/submodule-parallel-update:
clone: allow an explicit argument for parallel submodule clones
submodule update: expose parallelism to the user
submodule helper: remove double 'fatal: ' prefix
git submodule update: have a dedicated helper for cloning
run_processes_parallel: rename parameters for the callbacks
run_processes_parallel: treat output of children as byte array
submodule update: direct error message to stderr
fetching submodules: respect `submodule.fetchJobs` config option
submodule-config: drop check against NULL
submodule-config: keep update strategy around
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Simplify the two callback functions that are triggered when the
child process terminates to avoid misuse of the child-process
structure that has already been cleaned up.
* sb/submodule-parallel-fetch:
run-command: do not pass child process data into callbacks
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The refs code has a similar pattern of passing around 'struct strbuf *err',
which is strictly used for error reporting. This is not the case here,
as the strbuf is used to accumulate all the output (whether it is error
or not) for the user. Rename it to 'out'.
Suggested-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The expected way to pass data into the callback is to pass them via
the customizable callback pointer. The error reporting in
default_{start_failure, task_finished} is not user friendly enough, that
we want to encourage using the child data for such purposes.
Furthermore the struct child data is cleaned by the run-command API,
before we access them in the callbacks, leading to use-after-free
situations.
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Handling of errors while writing into our internal asynchronous
process has been made more robust, which reduces flakiness in our
tests.
* jk/epipe-in-async:
t5504: handle expected output from SIGPIPE death
test_must_fail: report number of unexpected signal
fetch-pack: ignore SIGPIPE in sideband demuxer
write_or_die: handle EPIPE in async threads
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When write_or_die() sees EPIPE, it treats it specially by
converting it into a SIGPIPE death. We obviously cannot
ignore it, as the write has failed and the caller expects us
to die. But likewise, we cannot just call die(), because
printing any message at all would be a nuisance during
normal operations.
However, this is a problem if write_or_die() is called from
a thread. Our raised signal ends up killing the whole
process, when logically we just need to kill the thread
(after all, if we are ignoring SIGPIPE, there is good reason
to think that the main thread is expecting to handle it).
Inside an async thread, the die() code already does the
right thing, because we use our custom die_async() routine,
which calls pthread_join(). So ideally we would piggy-back
on that, and simply call:
die_quietly_with_code(141);
or similar. But refactoring the die code to do this is
surprisingly non-trivial. The die_routines themselves handle
both printing and the decision of the exit code. Every one
of them would have to be modified to take new parameters for
the code, and to tell us to be quiet.
Instead, we can just teach write_or_die() to check for the
async case and handle it specially. We do have to build an
interface to abstract the async exit, but it's simple and
self-contained. If we had many call-sites that wanted to do
this die_quietly_with_code(), this approach wouldn't scale
as well, but we don't. This is the only place where do this
weird exit trick.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This allows to run external commands in parallel with ordered output
on stderr.
If we run external commands in parallel we cannot pipe the output directly
to the our stdout/err as it would mix up. So each process's output will
flow through a pipe, which we buffer. One subprocess can be directly
piped to out stdout/err for a low latency feedback to the user.
Example:
Let's assume we have 5 submodules A,B,C,D,E and each fetch takes a
different amount of time as the different submodules vary in size, then
the output of fetches in sequential order might look like this:
time -->
output: |---A---| |-B-| |-------C-------| |-D-| |-E-|
When we schedule these submodules into maximal two parallel processes,
a schedule and sample output over time may look like this:
process 1: |---A---| |-D-| |-E-|
process 2: |-B-| |-------C-------|
output: |---A---|B|---C-------|DE
So A will be perceived as it would run normally in the single child
version. As B has finished by the time A is done, we can dump its whole
progress buffer on stderr, such that it looks like it finished in no
time. Once that is done, C is determined to be the visible child and
its progress will be reported in real time.
So this way of output is really good for human consumption, as it only
changes the timing, not the actual output.
For machine consumption the output needs to be prepared in the tasks,
by either having a prefix per line or per block to indicate whose tasks
output is displayed, because the output order may not follow the
original sequential ordering:
|----A----| |--B--| |-C-|
will be scheduled to be all parallel:
process 1: |----A----|
process 2: |--B--|
process 3: |-C-|
output: |----A----|CB
This happens because C finished before B did, so it will be queued for
output before B.
To detect when a child has finished executing, we check interleaved
with other actions (such as checking the liveliness of children or
starting new processes) whether the stderr pipe still exists. Once a
child closed its stderr stream, we assume it is terminating very soon,
and use `finish_command()` from the single external process execution
interface to collect the exit status.
By maintaining the strong assumption of stderr being open until the
very end of a child process, we can avoid other hassle such as an
implementation using `waitpid(-1)`, which is not implemented in Windows.
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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"git daemon" uses "run_command()" without "finish_command()", so it
needs to release resources itself, which it forgot to do.
* rs/daemon-plug-child-leak:
daemon: plug memory leak
run-command: factor out child_process_clear()
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Avoid duplication by moving the code to release allocated memory for
arguments and environment to its own function, child_process_clear().
Export it to provide a counterpart to child_process_init().
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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