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Don't hold the xlib-xcb lock while sleeping: that allows deadlock. 

With this patch, `ico -threads 2` runs without deadlock.

Many thanks to Christoph Pfister <christophpfister@gmail.com> for
pointing out the problem, providing detailed analyses, explaining it to
me repeatedly until I understood what was going on, and proposing and
reviewing possible solutions.

Signed-off-by: Jamey Sharp <jamey@minilop.net>
Acked-by: Christoph Pfister <christophpfister@gmail.com>
This commit is contained in:
Jamey Sharp 2007-10-28 13:28:18 -07:00
parent f6b75d6090
commit a29fbc2645
1 changed files with 25 additions and 1 deletions
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26
src/xcb_conn.c
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@ -290,12 +290,25 @@ void _xcb_unlock_io(xcb_connection_t *c)
void _xcb_wait_io(xcb_connection_t *c, pthread_cond_t *cond) void _xcb_wait_io(xcb_connection_t *c, pthread_cond_t *cond)
{ {
int xlib_locked = c->xlib.lock;
if(xlib_locked)
{
c->xlib.lock = 0;
pthread_cond_broadcast(&c->xlib.cond);
}
pthread_cond_wait(cond, &c->iolock); pthread_cond_wait(cond, &c->iolock);
if(xlib_locked)
{
while(c->xlib.lock)
pthread_cond_wait(&c->xlib.cond, &c->iolock);
c->xlib.lock = 1;
c->xlib.thread = pthread_self();
}
} }
int _xcb_conn_wait(xcb_connection_t *c, pthread_cond_t *cond, struct iovec **vector, int *count) int _xcb_conn_wait(xcb_connection_t *c, pthread_cond_t *cond, struct iovec **vector, int *count)
{ {
int ret; int ret, xlib_locked;
fd_set rfds, wfds; fd_set rfds, wfds;
/* If the thing I should be doing is already being done, wait for it. */ /* If the thing I should be doing is already being done, wait for it. */
@ -316,6 +329,12 @@ int _xcb_conn_wait(xcb_connection_t *c, pthread_cond_t *cond, struct iovec **vec
++c->out.writing; ++c->out.writing;
} }
xlib_locked = c->xlib.lock;
if(xlib_locked)
{
c->xlib.lock = 0;
pthread_cond_broadcast(&c->xlib.cond);
}
_xcb_unlock_io(c); _xcb_unlock_io(c);
do { do {
ret = select(c->fd + 1, &rfds, &wfds, 0, 0); ret = select(c->fd + 1, &rfds, &wfds, 0, 0);
@ -326,6 +345,11 @@ int _xcb_conn_wait(xcb_connection_t *c, pthread_cond_t *cond, struct iovec **vec
ret = 0; ret = 0;
} }
_xcb_lock_io(c); _xcb_lock_io(c);
if(xlib_locked)
{
c->xlib.lock = 1;
c->xlib.thread = pthread_self();
}
if(ret) if(ret)
{ {