Commit 20ca2e94 authored by Troels Nielsen's avatar Troels Nielsen Committed by Chong Yidong

Ensure correct ordering of process writes.

* process.c (make_process): Initialize write_queue.
(write_queue_push, write_queue_pop): New functions.
(send_process): Use them to maintain correct ordering of process writes.

Fixes: debbugs:10815
parent 48d1354e
2012-06-17 Troels Nielsen <>
* process.c (make_process): Initialize write_queue.
(write_queue_push, write_queue_pop): New functions.
(send_process): Use them to maintain correct ordering of process
writes (Bug#10815).
2012-06-17 Paul Eggert <>
* lisp.h (eassert): Assume C89 or later.
......@@ -638,6 +638,7 @@ make_process (Lisp_Object name)
p->status = Qrun;
p->mark = Fmake_marker ();
p->kill_without_query = 0;
p->write_queue = Qnil;
p->adaptive_read_buffering = 0;
......@@ -5371,6 +5372,78 @@ send_process_trap (int ignore)
longjmp (send_process_frame, 1);
/* In send_process, when a write fails temporarily,
wait_reading_process_output is called. It may execute user code,
e.g. timers, that attempts to write new data to the same process.
We must ensure that data is sent in the right order, and not
interspersed half-completed with other writes (Bug#10815). This is
handled by the write_queue element of struct process. It is a list
with each entry having the form
(string . (offset . length))
where STRING is a lisp string, OFFSET is the offset into the
string's byte sequence from which we should begin to send, and
LENGTH is the number of bytes left to send. */
/* Create a new entry in write_queue.
INPUT_OBJ should be a buffer, string Qt, or Qnil.
BUF is a pointer to the string sequence of the input_obj or a C
string in case of Qt or Qnil. */
static void
write_queue_push (struct Lisp_Process *p, Lisp_Object input_obj,
const char *buf, int len, int front)
EMACS_INT offset;
Lisp_Object entry, obj;
if (STRINGP (input_obj))
offset = buf - SSDATA (input_obj);
obj = input_obj;
offset = 0;
obj = make_unibyte_string (buf, len);
entry = Fcons (obj, Fcons (make_number (offset), make_number (len)));
if (front)
p->write_queue = Fcons (entry, p->write_queue);
p->write_queue = nconc2 (p->write_queue, Fcons (entry, Qnil));
/* Remove the first element in the write_queue of process P, put its
contents in OBJ, BUF and LEN, and return non-zero. If the
write_queue is empty, return zero. */
static int
write_queue_pop (struct Lisp_Process *p, Lisp_Object *obj,
const char **buf, EMACS_INT *len)
Lisp_Object entry, offset_length;
EMACS_INT offset;
if (NILP (p->write_queue))
return 0;
entry = XCAR (p->write_queue);
p->write_queue = XCDR (p->write_queue);
*obj = XCAR (entry);
offset_length = XCDR (entry);
*len = XINT (XCDR (offset_length));
offset = XINT (XCAR (offset_length));
*buf = SDATA (*obj) + offset;
return 1;
/* Send some data to process PROC.
BUF is the beginning of the data; LEN is the number of characters.
OBJECT is the Lisp object that the data comes from. If OBJECT is
......@@ -5389,11 +5462,8 @@ send_process (volatile Lisp_Object proc, const char *volatile buf,
struct Lisp_Process *p = XPROCESS (proc);
ssize_t rv;
struct coding_system *coding;
struct gcpro gcpro1;
void (*volatile old_sigpipe) (int);
GCPRO1 (object);
if (p->raw_status_new)
update_status (p);
if (! EQ (p->status, Qrun))
......@@ -5505,22 +5575,37 @@ send_process (volatile Lisp_Object proc, const char *volatile buf,
if (!setjmp (send_process_frame))
p = XPROCESS (proc); /* Repair any setjmp clobbering. */
process_sent_to = proc;
while (len > 0)
/* If there is already data in the write_queue, put the new data
in the back of queue. Otherwise, ignore it. */
if (!NILP (p->write_queue))
write_queue_push (p, object, buf, len, 0);
do /* while !NILP (p->write_queue) */
ptrdiff_t this = len;
EMACS_INT cur_len = -1;
const char *cur_buf;
Lisp_Object cur_object;
/* If write_queue is empty, ignore it. */
if (!write_queue_pop (p, &cur_object, &cur_buf, &cur_len))
cur_len = len;
cur_buf = buf;
cur_object = object;
/* Send this batch, using one or more write calls. */
while (this > 0)
while (cur_len > 0)
/* Send this batch, using one or more write calls. */
ptrdiff_t written = 0;
int outfd = p->outfd;
old_sigpipe = (void (*) (int)) signal (SIGPIPE, send_process_trap);
if (DATAGRAM_CHAN_P (outfd))
rv = sendto (outfd, buf, this,
rv = sendto (outfd, cur_buf, cur_len,
0, datagram_address[outfd].sa,
if (0 <= rv)
......@@ -5537,10 +5622,10 @@ send_process (volatile Lisp_Object proc, const char *volatile buf,
if (p->gnutls_p)
written = emacs_gnutls_write (p, buf, this);
written = emacs_gnutls_write (p, cur_buf, cur_len);
written = emacs_write (outfd, buf, this);
written = emacs_write (outfd, cur_buf, cur_len);
rv = (written ? 0 : -1);
if (p->read_output_delay > 0
......@@ -5595,35 +5680,26 @@ send_process (volatile Lisp_Object proc, const char *volatile buf,
/* Running filters might relocate buffers or strings.
Arrange to relocate BUF. */
if (BUFFERP (object))
offset = BUF_PTR_BYTE_POS (XBUFFER (object),
(unsigned char *) buf);
else if (STRINGP (object))
offset = buf - SSDATA (object);
/* Put what we should have written in
wait_queue */
write_queue_push (p, cur_object, cur_buf, cur_len, 1);
wait_reading_process_output (0, 20000, 0, 0, Qnil, NULL, 0);
wait_reading_process_output (1, 0, 0, 0, Qnil, NULL, 0);
if (BUFFERP (object))
buf = (char *) BUF_BYTE_ADDRESS (XBUFFER (object),
else if (STRINGP (object))
buf = offset + SSDATA (object);
/* reread queue, to see what is left */
/* This is a real error. */
report_file_error ("writing to process", Fcons (proc, Qnil));
buf += written;
len -= written;
this -= written;
cur_buf += written;
cur_len -= written;
while (!NILP (p->write_queue));
......@@ -5636,8 +5712,6 @@ send_process (volatile Lisp_Object proc, const char *volatile buf,
deactivate_process (proc);
error ("SIGPIPE raised on process %s; closed it", SDATA (p->name));
DEFUN ("process-send-region", Fprocess_send_region, Sprocess_send_region,
......@@ -77,6 +77,8 @@ struct Lisp_Process
Lisp_Object encode_coding_system;
/* Working buffer for encoding. */
Lisp_Object encoding_buf;
/* Queue for storing waiting writes */
Lisp_Object write_queue;
Lisp_Object gnutls_cred_type;
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