run-command: allow stdin for run_processes_parallel
While it makes sense not to inherit stdin from the parent process to avoid deadlocking, it's not necessary to completely ban stdin to children. An informed user should be able to configure stdin safely. By setting `some_child.process.no_stdin=1` before calling `get_next_task()` we provide a reasonable default behavior but enable users to set up stdin streaming for themselves during the callback. `some_child.process.stdout_to_stderr`, however, remains unmodifiable by `get_next_task()` - the rest of the run_processes_parallel() API depends on child output in stderr. 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>
Emily Shaffer committed
Feb 8, 2023 at 20:21 UTC
540267304d37d6257edb3144e770693071d8fbb7
1 file changed
+8
-1
run-command.c
+8
-1
index b439c7974c..6bd16acb06 100644
--- a/run-command.c
+++ b/run-command.c
@@ -1586,6 +1586,14 @@ static int pp_start_one(struct parallel_processes *pp,
if (i == opts->processes)
BUG("bookkeeping is hard");
+ /*
+ * By default, do not inherit stdin from the parent process - otherwise,
+ * all children would share stdin! Users may overwrite this to provide
+ * something to the child's stdin by having their 'get_next_task'
+ * callback assign 0 to .no_stdin and an appropriate integer to .in.
+ */
+ pp->children[i].process.no_stdin = 1;
+
code = opts->get_next_task(&pp->children[i].process,
opts->ungroup ? NULL : &pp->children[i].err,
opts->data,
@@ -1601,7 +1609,6 @@ static int pp_start_one(struct parallel_processes *pp,
pp->children[i].process.err = -1;
pp->children[i].process.stdout_to_stderr = 1;
}
- pp->children[i].process.no_stdin = 1;
if (start_command(&pp->children[i].process)) {
if (opts->start_failure)