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Switch sequence comparisons to handle 32-bit sequence number wrap. 

Create a macro, XCB_SEQUENCE_COMPARE, that accepts two sequence numbers and
a comparison operator and correctly handles 32-bit wrap around.
Rewrite all ordered sequence number comparisons to use this macro.
Also, caught one error where a sequence was stored in a signed int variable.
Push out a GetInputFocus request when the sequence number does wrap at 32
bits so that applications cannot see sequence 0 (as that is an error
indicator).
This commit is contained in:
Keith Packard 2006-07-01 00:16:07 -07:00
parent 75fead5b86
commit db2504130b
3 changed files with 39 additions and 15 deletions
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32
src/xcb_in.c
View File

@ -91,11 +91,11 @@ static int read_packet(XCBConnection *c)
/* Compute 32-bit sequence number of this packet. */
if((genrep.response_type & 0x7f) != XCBKeymapNotify)
{
int lastread = c->in.request_read;
unsigned int lastread = c->in.request_read;
c->in.request_read = (lastread & 0xffff0000) | genrep.sequence;
if(c->in.request_read < lastread)
if(XCB_SEQUENCE_COMPARE(c->in.request_read, <, lastread))
c->in.request_read += 0x10000;
if(c->in.request_read > c->in.request_expected)
if(XCB_SEQUENCE_COMPARE(c->in.request_read, >, c->in.request_expected))
c->in.request_expected = c->in.request_read;
if(c->in.request_read != lastread)
@ -111,7 +111,8 @@ static int read_packet(XCBConnection *c)
if(genrep.response_type != XCBReply) /* error or event */
c->in.request_completed = c->in.request_read; /* XXX: does event/error imply no more replies? */
while(c->in.pending_replies && c->in.pending_replies->request <= c->in.request_completed)
while(c->in.pending_replies &&
XCB_SEQUENCE_COMPARE (c->in.pending_replies->request, <=, c->in.request_completed))
{
pending_reply *oldpend = c->in.pending_replies;
c->in.pending_replies = oldpend->next;
@ -168,12 +169,17 @@ static int read_packet(XCBConnection *c)
cur->next = 0;
*c->in.current_reply_tail = cur;
c->in.current_reply_tail = &cur->next;
for(reader = c->in.readers; reader && reader->request <= c->in.request_read; reader = reader->next)
for(reader = c->in.readers;
reader &&
XCB_SEQUENCE_COMPARE(reader->request, <=, c->in.request_read);
reader = reader->next)
{
if(reader->request == c->in.request_read)
{
pthread_cond_signal(reader->data);
break;
}
}
return 1;
}
@ -249,7 +255,7 @@ static int poll_for_reply(XCBConnection *c, unsigned int request, void **reply,
head = 0;
/* We've read requests past the one we want, so if it has replies we have
* them all and they're in the replies map. */
else if(request < c->in.request_read)
else if(XCB_SEQUENCE_COMPARE(request, <, c->in.request_read))
{
head = _xcb_map_remove(c->in.replies, request);
if(head && head->next)
@ -312,8 +318,13 @@ void *XCBWaitForReply(XCBConnection *c, unsigned int request, XCBGenericError **
reader_list reader;
reader_list **prev_reader;
for(prev_reader = &c->in.readers; *prev_reader && (*prev_reader)->request <= request; prev_reader = &(*prev_reader)->next)
for(prev_reader = &c->in.readers;
*prev_reader &&
XCB_SEQUENCE_COMPARE ((*prev_reader)->request, <=, request);
prev_reader = &(*prev_reader)->next)
{
/* empty */;
}
reader.request = request;
reader.data = &cond;
reader.next = *prev_reader;
@ -323,12 +334,17 @@ void *XCBWaitForReply(XCBConnection *c, unsigned int request, XCBGenericError **
if(!_xcb_conn_wait(c, &cond, 0, 0))
break;
for(prev_reader = &c->in.readers; *prev_reader && (*prev_reader)->request <= request; prev_reader = &(*prev_reader)->next)
for(prev_reader = &c->in.readers;
*prev_reader &&
XCB_SEQUENCE_COMPARE((*prev_reader)->request, <=, request);
prev_reader = &(*prev_reader)->next)
{
if(*prev_reader == &reader)
{
*prev_reader = (*prev_reader)->next;
break;
}
}
pthread_cond_destroy(&cond);
}

20
src/xcb_out.c
View File

@ -157,16 +157,22 @@ unsigned int XCBSendRequest(XCBConnection *c, int flags, struct iovec *vector, c
while(c->out.writing)
pthread_cond_wait(&c->out.cond, &c->iolock);
if(req->isvoid && c->out.request == c->in.request_expected + (1 << 16) - 2)
request = ++c->out.request;
/* send GetInputFocus (sync) when 64k-2 requests have been sent without
* a reply.
* Also send sync (could use NoOp) at 32-bit wrap to avoid having
* applications see sequence 0 as that is used to indicate
* an error in sending the request */
if((req->isvoid &&
c->out.request == c->in.request_expected + (1 << 16) - 2) ||
request == 0)
{
prefix[0] = sync.packet;
request = ++c->out.request;
_xcb_in_expect_reply(c, request, WORKAROUND_NONE, XCB_REQUEST_DISCARD_REPLY);
c->in.request_expected = c->out.request;
request = ++c->out.request;
}
request = ++c->out.request;
assert(request != 0);
if(workaround != WORKAROUND_NONE || flags != 0)
_xcb_in_expect_reply(c, request, workaround, flags);
if(!req->isvoid)
@ -238,8 +244,8 @@ int _xcb_out_send(XCBConnection *c, struct iovec **vector, int *count)
int _xcb_out_flush_to(XCBConnection *c, unsigned int request)
{
assert(request <= c->out.request);
if(c->out.request_written >= request)
assert(XCB_SEQUENCE_COMPARE(request, <=, c->out.request));
if(XCB_SEQUENCE_COMPARE(c->out.request_written, >=, request))
return 1;
if(c->out.queue_len)
{
@ -252,6 +258,6 @@ int _xcb_out_flush_to(XCBConnection *c, unsigned int request)
}
while(c->out.writing)
pthread_cond_wait(&c->out.cond, &c->iolock);
assert(c->out.request_written >= request);
assert(XCB_SEQUENCE_COMPARE(c->out.request_written, >=, request));
return 1;
}

2
src/xcbint.h
View File

@ -43,6 +43,8 @@ enum workarounds {
#define XCB_PAD(i) (-(i) & 3)
#define XCB_SEQUENCE_COMPARE(a,op,b) ((int) ((a) - (b)) op 0)
/* xcb_list.c */
typedef void (*XCBListFreeFunc)(void *);