From db2504130bc450bd328830060cb3a243dd06b52f Mon Sep 17 00:00:00 2001 From: Keith Packard Date: Sat, 1 Jul 2006 00:16:07 -0700 Subject: [PATCH] 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). --- src/xcb_in.c | 32 ++++++++++++++++++++++++-------- src/xcb_out.c | 20 +++++++++++++------- src/xcbint.h | 2 ++ 3 files changed, 39 insertions(+), 15 deletions(-) diff --git a/src/xcb_in.c b/src/xcb_in.c index 3bf54f3..6433f0e 100644 --- a/src/xcb_in.c +++ b/src/xcb_in.c @@ -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); } diff --git a/src/xcb_out.c b/src/xcb_out.c index f12a071..9a67ad2 100644 --- a/src/xcb_out.c +++ b/src/xcb_out.c @@ -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; } diff --git a/src/xcbint.h b/src/xcbint.h index a6d92aa..9048e9d 100644 --- a/src/xcbint.h +++ b/src/xcbint.h @@ -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 *); -- 2.34.1