From 972dcfcdbfe75dcfeb777150c136576cf1a71e99 Mon Sep 17 00:00:00 2001 From: Tudor Florea Date: Fri, 9 Oct 2015 22:59:03 +0200 Subject: initial commit for Enea Linux 5.0 arm Signed-off-by: Tudor Florea --- ...owns-socket-and-no-other-threads-are-writ.patch | 121 +++++++++++++++++++++ 1 file changed, 121 insertions(+) create mode 100644 meta/recipes-graphics/xorg-lib/libxcb/ensure-xcb-owns-socket-and-no-other-threads-are-writ.patch (limited to 'meta/recipes-graphics/xorg-lib/libxcb/ensure-xcb-owns-socket-and-no-other-threads-are-writ.patch') diff --git a/meta/recipes-graphics/xorg-lib/libxcb/ensure-xcb-owns-socket-and-no-other-threads-are-writ.patch b/meta/recipes-graphics/xorg-lib/libxcb/ensure-xcb-owns-socket-and-no-other-threads-are-writ.patch new file mode 100644 index 0000000000..14cefa3f29 --- /dev/null +++ b/meta/recipes-graphics/xorg-lib/libxcb/ensure-xcb-owns-socket-and-no-other-threads-are-writ.patch @@ -0,0 +1,121 @@ +From be0fe56c3bcad5124dcc6c47a2fad01acd16f71a Mon Sep 17 00:00:00 2001 +From: Keith Packard +Date: Mon, 23 Dec 2013 21:15:20 -0800 +Subject: [PATCH] Ensure xcb owns socket and no other threads are writing + before send_request + +send_request may only write to out.queue if no other thread is busy +writing to the network (as that thread may be writing from out.queue). + +send_request may only allocate request sequence numbers if XCB owns +the socket. + +Therefore, send_request must make sure that both conditions are true +when it holds iolock, which can only be done by looping until both +conditions are true without having dropped the lock waiting for the +second condition. + +We choose to get the socket back from Xlib first as get_socket_back +has a complicated test and checking for other threads writing is a +simple in-lined check. + +This also changes the sequence number checks (64k requests with no +reply, 4M request wrapping) to ensure that both conditions are true +before queueing the request. + +Signed-off-by: Keith Packard +Reviewed-by: Uli Schlachter +--- + src/xcb_out.c | 57 ++++++++++++++++++++++++++++++++++++++++----------------- + 1 file changed, 40 insertions(+), 17 deletions(-) + +diff --git a/src/xcb_out.c b/src/xcb_out.c +index 18bb5f9..dc42954 100644 +--- a/src/xcb_out.c ++++ b/src/xcb_out.c +@@ -103,6 +103,33 @@ static void get_socket_back(xcb_connection_t *c) + _xcb_in_replies_done(c); + } + ++static void prepare_socket_request(xcb_connection_t *c) ++{ ++ /* We're about to append data to out.queue, so we need to ++ * atomically test for an external socket owner *and* some other ++ * thread currently writing. ++ * ++ * If we have an external socket owner, we have to get the socket back ++ * before we can use it again. ++ * ++ * If some other thread is writing to the socket, we assume it's ++ * writing from out.queue, and so we can't stick data there. ++ * ++ * We satisfy this condition by first calling get_socket_back ++ * (which may drop the lock, but will return when XCB owns the ++ * socket again) and then checking for another writing thread and ++ * escaping the loop if we're ready to go. ++ */ ++ for (;;) { ++ if(c->has_error) ++ return; ++ get_socket_back(c); ++ if (!c->out.writing) ++ break; ++ pthread_cond_wait(&c->out.cond, &c->iolock); ++ } ++} ++ + /* Public interface */ + + void xcb_prefetch_maximum_request_length(xcb_connection_t *c) +@@ -236,24 +263,23 @@ unsigned int xcb_send_request(xcb_connection_t *c, int flags, struct iovec *vect + + /* get a sequence number and arrange for delivery. */ + pthread_mutex_lock(&c->iolock); +- /* wait for other writing threads to get out of my way. */ +- while(c->out.writing) +- pthread_cond_wait(&c->out.cond, &c->iolock); +- get_socket_back(c); ++ ++ prepare_socket_request(c); + + /* send GetInputFocus (sync_req) when 64k-2 requests have been sent without +- * a reply. */ +- if(req->isvoid && c->out.request == c->in.request_expected + (1 << 16) - 2) +- send_sync(c); +- /* Also send sync_req (could use NoOp) at 32-bit wrap to avoid having ++ * a reply. ++ * Also send sync_req (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((unsigned int) (c->out.request + 1) == 0) ++ * an error in sending the request ++ */ ++ ++ while ((req->isvoid && c->out.request == c->in.request_expected + (1 << 16) - 2) || ++ (unsigned int) (c->out.request + 1) == 0) ++ { + send_sync(c); ++ prepare_socket_request(c); ++ } + +- /* The above send_sync calls could drop the I/O lock, but this +- * thread will still exclude any other thread that tries to write, +- * so the sequence number postconditions still hold. */ + send_request(c, req->isvoid, workaround, flags, vector, veclen); + request = c->has_error ? 0 : c->out.request; + pthread_mutex_unlock(&c->iolock); +@@ -373,10 +399,7 @@ int _xcb_out_send(xcb_connection_t *c, struct iovec *vector, int count) + + void _xcb_out_send_sync(xcb_connection_t *c) + { +- /* wait for other writing threads to get out of my way. */ +- while(c->out.writing) +- pthread_cond_wait(&c->out.cond, &c->iolock); +- get_socket_back(c); ++ prepare_socket_request(c); + send_sync(c); + } + +-- +1.9.1 + -- cgit v1.2.3-54-g00ecf