Commit 35fb8050 authored by Paul Eggert's avatar Paul Eggert

Fix a recently-introduced delete-process race condition.

* callproc.c, process.h (record_kill_process):
New function, containing part of the old call_process_kill.
(call_process_kill): Use it.
This does not change call_process_kill's behavior.
* process.c (Fdelete_process): Use record_kill_process to fix a
race condition that could cause Emacs to lose track of a child.
parent 565212e5
2012-12-06 Paul Eggert <eggert@cs.ucla.edu>
Fix a recently-introduced delete-process race condition.
* callproc.c, process.h (record_kill_process):
New function, containing part of the old call_process_kill.
(call_process_kill): Use it.
This does not change call_process_kill's behavior.
* process.c (Fdelete_process): Use record_kill_process to fix a
race condition that could cause Emacs to lose track of a child.
2012-12-06 Dmitry Antipov <dmantipov@yandex.ru>
Avoid code duplication between prev_frame and next_frame.
......
......@@ -105,6 +105,25 @@ unblock_child_signal (void)
#endif
}
/* If P is reapable, record it as a deleted process and kill it.
Do this in a critical section. Unless PID is wedged it will be
reaped on receipt of the first SIGCHLD after the critical section. */
void
record_kill_process (struct Lisp_Process *p)
{
block_child_signal ();
if (p->alive)
{
p->alive = 0;
record_deleted_pid (p->pid);
EMACS_KILLPG (p->pid, SIGKILL);
}
unblock_child_signal ();
}
/* Clean up when exiting call_process_cleanup. */
static Lisp_Object
......@@ -113,15 +132,12 @@ call_process_kill (Lisp_Object ignored)
if (0 <= synch_process_fd)
emacs_close (synch_process_fd);
/* If PID is reapable, kill it and record it as a deleted process.
Do this in a critical section. Unless PID is wedged it will be
reaped on receipt of the first SIGCHLD after the critical section. */
if (synch_process_pid)
{
block_child_signal ();
record_deleted_pid (synch_process_pid);
EMACS_KILLPG (synch_process_pid, SIGKILL);
unblock_child_signal ();
struct Lisp_Process proc;
proc.alive = 1;
proc.pid = synch_process_pid;
record_kill_process (&proc);
}
return Qnil;
......
......@@ -813,30 +813,22 @@ nil, indicating the current buffer's process. */)
status_notify (p);
redisplay_preserve_echo_area (13);
}
else if (p->infd >= 0)
else
{
#ifdef SIGCHLD
Lisp_Object symbol;
pid_t pid = p->pid;
/* No problem storing the pid here, as it is still in Vprocess_alist. */
record_deleted_pid (pid);
/* If the process has already signaled, remove it from the list. */
if (p->raw_status_new)
update_status (p);
symbol = p->status;
if (CONSP (p->status))
symbol = XCAR (p->status);
if (EQ (symbol, Qsignal) || EQ (symbol, Qexit))
deleted_pid_list
= Fdelete (make_fixnum_or_float (pid), deleted_pid_list);
else
#endif
if (p->alive)
record_kill_process (p);
if (p->infd >= 0)
{
Fkill_process (process, Qnil);
/* Do this now, since remove_process will make the
SIGCHLD handler do nothing. */
pset_status (p, Fcons (Qsignal, Fcons (make_number (SIGKILL), Qnil)));
/* Update P's status, since record_kill_process will make the
SIGCHLD handler update deleted_pid_list, not *P. */
Lisp_Object symbol;
if (p->raw_status_new)
update_status (p);
symbol = CONSP (p->status) ? XCAR (p->status) : p->status;
if (! (EQ (symbol, Qsignal) || EQ (symbol, Qexit)))
pset_status (p, list2 (Qsignal, make_number (SIGKILL)));
p->tick = ++process_tick;
status_notify (p);
redisplay_preserve_echo_area (13);
......
......@@ -198,6 +198,12 @@ extern Lisp_Object QCspeed;
extern Lisp_Object QCbytesize, QCstopbits, QCparity, Qodd, Qeven;
extern Lisp_Object QCflowcontrol, Qhw, Qsw, QCsummary;
/* Defined in callproc.c. */
extern void record_kill_process (struct Lisp_Process *);
/* Defined in process.c. */
extern Lisp_Object list_system_processes (void);
extern Lisp_Object system_process_attributes (Lisp_Object);
......
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