From c549a40547fb9765a9ea78dbe4a3397dbee715b2 Mon Sep 17 00:00:00 2001 From: Adrian Ratiu Date: Wed, 28 Jan 2026 23:39:24 +0200 Subject: [PATCH] hook: add jobs option Allow the API callers to specify the number of jobs across which hook execution can be parallelized. It defaults to 1 and no hook currently changes it, so all hooks run sequentially as before. This allows us to both pave the way for parallel hook execution (that will be a follow-up patch series building upon this) and to finish the API conversion of builtin/receive-pack.c, keeping the output async sideband thread ("muxer") design as Peff suggested. When .jobs==1 nothing changes, the "copy_to_sideband" async thread still outputs directly via sideband channel 2, keeping the current (mostly) real-time output characteristics, avoids unnecessary poll delays or deadlock risks. When .jobs > 1, a more complex muxer is needed to buffer the hook output and avoid interleaving. After working on this mux I quickly realized I was re-implementing run-command with ungroup=0 so that idea was dropped in favor of run-command which outputs to stderr. In other words, run-command itself already can buffer/deinterleave pp child outputs (ungroup=0), so we can just connect its stderr to the sideband async task when jobs > 1. Maybe it helps to illustrate how it works with ascii graphics: [ Sequential (jobs = 1) ] [ Parallel (jobs > 1) ] +--------------+ +--------+ +--------+ | Hook Process | | Hook 1 | | Hook 2 | +--------------+ +--------+ +--------+ | | | | stderr (inherited) | stderr pipe | | | (captured) | v v v +-------------------------------------------------------------+ | Parent Process | | | | (direct write) [run-command (buffered)] | | | | | | | | writes | | v v | | +-------------------------------------------+ | | | stderr (FD 2) | | | +-------------------------------------------+ | | | | | | (dup2'd to pipe) | | v | | +-----------------------+ | | | sideband async thread | | | +-----------------------+ | +-------------------------------------------------------------+ When use_sideband == 0, the sideband async thread is missing, so this same architecture just outputs via the parent stderr stream. See the following commits for the hook API conversions doing this, using pre-existing sideband thread logic from `copy_to_sideband`. Suggested-by: Jeff King Signed-off-by: Adrian Ratiu Signed-off-by: Junio C Hamano --- hook.c | 7 +++++-- hook.h | 9 +++++++++ 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/hook.c b/hook.c index fde1f88ce8..cde7198412 100644 --- a/hook.c +++ b/hook.c @@ -152,8 +152,8 @@ int run_hooks_opt(struct repository *r, const char *hook_name, .tr2_category = "hook", .tr2_label = hook_name, - .processes = 1, - .ungroup = 1, + .processes = options->jobs, + .ungroup = options->jobs == 1, .get_next_task = pick_next_hook, .start_failure = notify_start_failure, @@ -169,6 +169,9 @@ int run_hooks_opt(struct repository *r, const char *hook_name, if (options->path_to_stdin && options->feed_pipe) BUG("options path_to_stdin and feed_pipe are mutually exclusive"); + if (!options->jobs) + BUG("run_hooks_opt must be called with options.jobs >= 1"); + if (options->invoked_hook) *options->invoked_hook = 0; diff --git a/hook.h b/hook.h index 2c8a23a569..20eb56fd63 100644 --- a/hook.h +++ b/hook.h @@ -16,6 +16,14 @@ struct run_hooks_opt /* Emit an error if the hook is missing */ unsigned int error_if_missing:1; + /** + * Number of processes to parallelize across. + * + * If > 1, output will be buffered and de-interleaved (ungroup=0). + * If == 1, output will be real-time (ungroup=1). + */ + unsigned int jobs; + /** * An optional initial working directory for the hook, * translates to "struct child_process"'s "dir" member. @@ -90,6 +98,7 @@ struct run_hooks_opt .env = STRVEC_INIT, \ .args = STRVEC_INIT, \ .stdout_to_stderr = 1, \ + .jobs = 1, \ } struct hook_cb_data {