frederik
/
libxcb
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Add xcb_send_request_with_fds() and *_with_fds64() 

Doing xcb_send_fd(), xcb_send_request() is racy. If two threads do this at the
same time, they could mix up their file descriptors. This commit makes it
possibly to fix this race by providing a single function which does everything
that is needed.

Signed-off-by: Uli Schlachter <psychon@znc.in>
This commit is contained in:
Uli Schlachter 2015-04-22 09:23:47 +02:00
parent cc04cfb41b
commit b15aa6bd4e
2 changed files with 90 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
src/xcb_out.c
View File

@ -214,15 +214,18 @@ static void send_fds(xcb_connection_t *c, int *fds, unsigned int num_fds)
close_fds(fds, num_fds);
}
uint64_t xcb_send_request64(xcb_connection_t *c, int flags, struct iovec *vector, const xcb_protocol_request_t *req)
uint64_t xcb_send_request_with_fds64(xcb_connection_t *c, int flags, struct iovec *vector,
const xcb_protocol_request_t *req, unsigned int num_fds, int *fds)
{
uint64_t request;
uint32_t prefix[2];
int veclen = req->count;
enum workarounds workaround = WORKAROUND_NONE;
if(c->has_error)
if(c->has_error) {
close_fds(fds, num_fds);
return 0;
}
assert(c != 0);
assert(vector != 0);
@ -241,6 +244,7 @@ uint64_t xcb_send_request64(xcb_connection_t *c, int flags, struct iovec *vector
const xcb_query_extension_reply_t *extension = xcb_get_extension_data(c, req->ext);
if(!(extension && extension->present))
{
close_fds(fds, num_fds);
_xcb_conn_shutdown(c, XCB_CONN_CLOSED_EXT_NOTSUPPORTED);
return 0;
}
@ -271,6 +275,7 @@ uint64_t xcb_send_request64(xcb_connection_t *c, int flags, struct iovec *vector
}
else if(longlen > xcb_get_maximum_request_length(c))
{
close_fds(fds, num_fds);
_xcb_conn_shutdown(c, XCB_CONN_CLOSED_REQ_LEN_EXCEED);
return 0; /* server can't take this; maybe need BIGREQUESTS? */
}
@ -317,12 +322,25 @@ uint64_t xcb_send_request64(xcb_connection_t *c, int flags, struct iovec *vector
prepare_socket_request(c);
}
send_fds(c, fds, num_fds);
send_request(c, req->isvoid, workaround, flags, vector, veclen);
request = c->has_error ? 0 : c->out.request;
pthread_mutex_unlock(&c->iolock);
return request;
}
/* request number are actually uint64_t internally but keep API compat with unsigned int */
unsigned int xcb_send_request_with_fds(xcb_connection_t *c, int flags, struct iovec *vector,
const xcb_protocol_request_t *req, unsigned int num_fds, int *fds)
{
return xcb_send_request_with_fds64(c, flags, vector, req, num_fds, fds);
}
uint64_t xcb_send_request64(xcb_connection_t *c, int flags, struct iovec *vector, const xcb_protocol_request_t *req)
{
return xcb_send_request_with_fds64(c, flags, vector, req, 0, NULL);
}
/* request number are actually uint64_t internally but keep API compat with unsigned int */
unsigned int xcb_send_request(xcb_connection_t *c, int flags, struct iovec *vector, const xcb_protocol_request_t *req)
{

77
src/xcbext.h
View File

@ -68,13 +68,13 @@ enum xcb_send_request_flags_t {
*
* This function sends a new request to the X server. The data of the request is
* given as an array of @c iovecs in the @p vector argument. The length of that
* array and the neccessary management information are given in the @p request
* array and the necessary management information are given in the @p request
* argument.
*
* When this function returns, the request might or might not be sent already.
* Use xcb_flush() to make sure that it really was sent.
*
* Please note that this function is not the prefered way for sending requests.
* Please note that this function is not the preferred way for sending requests.
* It's better to use the generated wrapper functions.
*
* Please note that xcb might use index -1 and -2 of the @p vector array internally,
@ -82,6 +82,37 @@ enum xcb_send_request_flags_t {
*/
unsigned int xcb_send_request(xcb_connection_t *c, int flags, struct iovec *vector, const xcb_protocol_request_t *request);
/**
* @brief Send a request to the server.
* @param c: The connection to the X server.
* @param flags: A combination of flags from the xcb_send_request_flags_t enumeration.
* @param vector: Data to send; must have two iovecs before start for internal use.
* @param request: Information about the request to be sent.
* @param num_fds: Number of additional file descriptors to send to the server
* @param fds: Additional file descriptors that should be send to the server.
* @return The request's sequence number on success, 0 otherwise.
*
* This function sends a new request to the X server. The data of the request is
* given as an array of @c iovecs in the @p vector argument. The length of that
* array and the necessary management information are given in the @p request
* argument.
*
* If @p num_fds is non-zero, @p fds points to an array of file descriptors that
* will be sent to the X server along with this request. After this function
* returns, all file descriptors sent are owned by xcb and will be closed
* eventually.
*
* When this function returns, the request might or might not be sent already.
* Use xcb_flush() to make sure that it really was sent.
*
* Please note that this function is not the preferred way for sending requests.
*
* Please note that xcb might use index -1 and -2 of the @p vector array internally,
* so they must be valid!
*/
unsigned int xcb_send_request_with_fds(xcb_connection_t *c, int flags, struct iovec *vector,
const xcb_protocol_request_t *request, unsigned int num_fds, int *fds);
/**
* @brief Send a request to the server, with 64-bit sequence number returned.
* @param c: The connection to the X server.
@ -92,13 +123,13 @@ unsigned int xcb_send_request(xcb_connection_t *c, int flags, struct iovec *vect
*
* This function sends a new request to the X server. The data of the request is
* given as an array of @c iovecs in the @p vector argument. The length of that
* array and the neccessary management information are given in the @p request
* array and the necessary management information are given in the @p request
* argument.
*
* When this function returns, the request might or might not be sent already.
* Use xcb_flush() to make sure that it really was sent.
*
* Please note that this function is not the prefered way for sending requests.
* Please note that this function is not the preferred way for sending requests.
* It's better to use the generated wrapper functions.
*
* Please note that xcb might use index -1 and -2 of the @p vector array internally,
@ -106,6 +137,38 @@ unsigned int xcb_send_request(xcb_connection_t *c, int flags, struct iovec *vect
*/
uint64_t xcb_send_request64(xcb_connection_t *c, int flags, struct iovec *vector, const xcb_protocol_request_t *request);
/**
* @brief Send a request to the server, with 64-bit sequence number returned.
* @param c: The connection to the X server.
* @param flags: A combination of flags from the xcb_send_request_flags_t enumeration.
* @param vector: Data to send; must have two iovecs before start for internal use.
* @param request: Information about the request to be sent.
* @param num_fds: Number of additional file descriptors to send to the server
* @param fds: Additional file descriptors that should be send to the server.
* @return The request's sequence number on success, 0 otherwise.
*
* This function sends a new request to the X server. The data of the request is
* given as an array of @c iovecs in the @p vector argument. The length of that
* array and the necessary management information are given in the @p request
* argument.
*
* If @p num_fds is non-zero, @p fds points to an array of file descriptors that
* will be sent to the X server along with this request. After this function
* returns, all file descriptors sent are owned by xcb and will be closed
* eventually.
*
* When this function returns, the request might or might not be sent already.
* Use xcb_flush() to make sure that it really was sent.
*
* Please note that this function is not the preferred way for sending requests.
* It's better to use the generated wrapper functions.
*
* Please note that xcb might use index -1 and -2 of the @p vector array internally,
* so they must be valid!
*/
uint64_t xcb_send_request_with_fds64(xcb_connection_t *c, int flags, struct iovec *vector,
const xcb_protocol_request_t *request, unsigned int num_fds, int *fds);
/**
* @brief Send a file descriptor to the server in the next call to xcb_send_request.
* @param c: The connection to the X server.
@ -114,9 +177,9 @@ uint64_t xcb_send_request64(xcb_connection_t *c, int flags, struct iovec *vector
* After this function returns, the file descriptor given is owned by xcb and
* will be closed eventually.
*
* FIXME: How the heck is this supposed to work in a thread-safe way? There is a
* race between two threads doing xcb_send_fd(); xcb_send_request(); at the same
* time.
* @deprecated This function cannot be used in a thread-safe way. Two threads
* that run xcb_send_fd(); xcb_send_request(); could mix up their file
* descriptors. Instead, xcb_send_request_with_fds() should be used.
*/
void xcb_send_fd(xcb_connection_t *c, int fd);