From: Jeff King <peff@xxxxxxxx>
When we spawn a helper process, it should generally be done
and finish_command called before we exit. However, if we
exit abnormally due to an early return or a signal, the
helper may continue to run in our absence.
In the best case, this may simply be wasted CPU cycles or a
few stray messages on a terminal. But it could also mean a
process that the user thought was aborted continues to run
to completion (e.g., a push's pack-objects helper will
complete the push, even though you killed the push process).
This patch provides infrastructure for run-command to keep
track of PIDs to be killed, and clean them on signal
reception or input, just as we do with tempfiles. PIDs can
be added in two ways:
1. If NO_PTHREADS is defined, async helper processes are
automatically marked. By definition this code must be
ready to die when the parent dies, since it may be
implemented as a thread of the parent process.
2. If the run-command caller specifies the "clean_on_exit"
option. This is not the default, as there are cases
where it is OK for the child to outlive us (e.g., when
spawning a pager).
PIDs are cleared from the kill-list automatically during
wait_or_whine, which is called from finish_command and
finish_async.
Signed-off-by: Clemens Buchacher <drizzd@xxxxxx>
---
Not sure if I can sign off without your sign-off. Should I have
replaced this with Acked-by?
run-command.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
run-command.h | 1 +
2 files changed, 69 insertions(+), 0 deletions(-)
diff --git a/run-command.c b/run-command.c
index 1c51043..0204aaf 100644
--- a/run-command.c
+++ b/run-command.c
@@ -1,8 +1,66 @@
#include "cache.h"
#include "run-command.h"
#include "exec_cmd.h"
+#include "sigchain.h"
#include "argv-array.h"
+struct child_to_clean {
+ pid_t pid;
+ struct child_to_clean *next;
+};
+static struct child_to_clean *children_to_clean;
+static int installed_child_cleanup_handler;
+
+static void cleanup_children(int sig)
+{
+ while (children_to_clean) {
+ struct child_to_clean *p = children_to_clean;
+ children_to_clean = p->next;
+ kill(p->pid, sig);
+ free(p);
+ }
+}
+
+static void cleanup_children_on_signal(int sig)
+{
+ cleanup_children(sig);
+ sigchain_pop(sig);
+ raise(sig);
+}
+
+static void cleanup_children_on_exit(void)
+{
+ cleanup_children(SIGTERM);
+}
+
+static void mark_child_for_cleanup(pid_t pid)
+{
+ struct child_to_clean *p = xmalloc(sizeof(*p));
+ p->pid = pid;
+ p->next = children_to_clean;
+ children_to_clean = p;
+
+ if (!installed_child_cleanup_handler) {
+ atexit(cleanup_children_on_exit);
+ sigchain_push_common(cleanup_children_on_signal);
+ installed_child_cleanup_handler = 1;
+ }
+}
+
+static void clear_child_for_cleanup(pid_t pid)
+{
+ struct child_to_clean **last, *p;
+
+ last = &children_to_clean;
+ for (p = children_to_clean; p; p = p->next) {
+ if (p->pid == pid) {
+ *last = p->next;
+ free(p);
+ return;
+ }
+ }
+}
+
static inline void close_pair(int fd[2])
{
close(fd[0]);
@@ -130,6 +188,9 @@ static int wait_or_whine(pid_t pid, const char *argv0, int silent_exec_failure)
} else {
error("waitpid is confused (%s)", argv0);
}
+
+ clear_child_for_cleanup(pid);
+
errno = failed_errno;
return code;
}
@@ -292,6 +353,8 @@ fail_pipe:
if (cmd->pid < 0)
error("cannot fork() for %s: %s", cmd->argv[0],
strerror(failed_errno = errno));
+ else if (cmd->clean_on_exit)
+ mark_child_for_cleanup(cmd->pid);
/*
* Wait for child's execvp. If the execvp succeeds (or if fork()
@@ -312,6 +375,7 @@ fail_pipe:
cmd->pid = -1;
}
close(notify_pipe[0]);
+
}
#else
{
@@ -356,6 +420,8 @@ fail_pipe:
failed_errno = errno;
if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
error("cannot spawn %s: %s", cmd->argv[0], strerror(errno));
+ if (cmd->clean_on_exit && cmd->pid >= 0)
+ mark_child_for_cleanup(cmd->pid);
if (cmd->env)
free_environ(env);
@@ -540,6 +606,8 @@ int start_async(struct async *async)
exit(!!async->proc(proc_in, proc_out, async->data));
}
+ mark_child_for_cleanup(async->pid);
+
if (need_in)
close(fdin[0]);
else if (async->in)
diff --git a/run-command.h b/run-command.h
index 56491b9..2a69466 100644
--- a/run-command.h
+++ b/run-command.h
@@ -38,6 +38,7 @@ struct child_process {
unsigned silent_exec_failure:1;
unsigned stdout_to_stderr:1;
unsigned use_shell:1;
+ unsigned clean_on_exit:1;
void (*preexec_cb)(void);
};
--
1.7.8
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