On Fri, 5 Feb 2016 14:44:29 +0100 Rui Matos <tiagoma...@gmail.com> wrote:
> Keeping the shm fd open beyond pixmap creation means we can easily > reach the open file descriptor limit if an X client asks us to create > that many pixmaps. Instead, let's get the wl_buffer immediatly so that > we can destroy the shm pool and close the fd before being asked to > create more. > --- > > On Fri, Feb 5, 2016 at 1:53 PM, Pekka Paalanen <ppaala...@gmail.com> wrote: > > You don't need the fd or the pool to write into the buffer, or attach > > and commit the wl_buffer, or... > > You are right, of course. My initial attempt at this was crashing and > I quickly dismissed this approach without investigating why it was > crashing more closely. And sure enough, it was just a thinko on my > part. > > Thanks! > > Rui > > hw/xwayland/xwayland-shm.c | 46 > +++++++++++++++++++--------------------------- > 1 file changed, 19 insertions(+), 27 deletions(-) > > diff --git a/hw/xwayland/xwayland-shm.c b/hw/xwayland/xwayland-shm.c > index 7072be4..25ee03c 100644 > --- a/hw/xwayland/xwayland-shm.c > +++ b/hw/xwayland/xwayland-shm.c > @@ -36,7 +36,6 @@ > > struct xwl_pixmap { > struct wl_buffer *buffer; > - int fd; > void *data; > size_t size; > }; > @@ -174,9 +173,13 @@ PixmapPtr > xwl_shm_create_pixmap(ScreenPtr screen, > int width, int height, int depth, unsigned int hint) > { > - PixmapPtr pixmap; > + struct xwl_screen *xwl_screen = xwl_screen_get(screen); > struct xwl_pixmap *xwl_pixmap; > + struct wl_shm_pool *pool; > + PixmapPtr pixmap; > size_t size, stride; > + uint32_t format; > + int fd; > > if (hint == CREATE_PIXMAP_USAGE_GLYPH_PICTURE || > (width == 0 && height == 0) || depth < 15) > @@ -194,12 +197,12 @@ xwl_shm_create_pixmap(ScreenPtr screen, > size = stride * height; > xwl_pixmap->buffer = NULL; > xwl_pixmap->size = size; > - xwl_pixmap->fd = os_create_anonymous_file(size); > - if (xwl_pixmap->fd < 0) > + fd = os_create_anonymous_file(size); > + if (fd < 0) > goto err_free_xwl_pixmap; > > xwl_pixmap->data = mmap(NULL, size, PROT_READ | PROT_WRITE, > - MAP_SHARED, xwl_pixmap->fd, 0); > + MAP_SHARED, fd, 0); > if (xwl_pixmap->data == MAP_FAILED) > goto err_close_fd; > > @@ -208,6 +211,15 @@ xwl_shm_create_pixmap(ScreenPtr screen, > stride, xwl_pixmap->data)) > goto err_munmap; > > + format = shm_format_for_depth(pixmap->drawable.depth); > + pool = wl_shm_create_pool(xwl_screen->shm, fd, xwl_pixmap->size); > + xwl_pixmap->buffer = wl_shm_pool_create_buffer(pool, 0, > + pixmap->drawable.width, > + pixmap->drawable.height, > + pixmap->devKind, format); > + wl_shm_pool_destroy(pool); > + close(fd); > + > xwl_pixmap_set_private(pixmap, xwl_pixmap); > > return pixmap; > @@ -215,7 +227,7 @@ xwl_shm_create_pixmap(ScreenPtr screen, > err_munmap: > munmap(xwl_pixmap->data, size); > err_close_fd: > - close(xwl_pixmap->fd); > + close(fd); > err_free_xwl_pixmap: > free(xwl_pixmap); > err_destroy_pixmap: > @@ -233,7 +245,6 @@ xwl_shm_destroy_pixmap(PixmapPtr pixmap) > if (xwl_pixmap->buffer) > wl_buffer_destroy(xwl_pixmap->buffer); > munmap(xwl_pixmap->data, xwl_pixmap->size); > - close(xwl_pixmap->fd); > free(xwl_pixmap); > } > > @@ -243,26 +254,7 @@ xwl_shm_destroy_pixmap(PixmapPtr pixmap) > struct wl_buffer * > xwl_shm_pixmap_get_wl_buffer(PixmapPtr pixmap) > { > - struct xwl_screen *xwl_screen = xwl_screen_get(pixmap->drawable.pScreen); > - struct xwl_pixmap *xwl_pixmap = xwl_pixmap_get(pixmap); > - struct wl_shm_pool *pool; > - uint32_t format; > - > - if (xwl_pixmap->buffer) > - return xwl_pixmap->buffer; > - > - pool = wl_shm_create_pool(xwl_screen->shm, > - xwl_pixmap->fd, xwl_pixmap->size); > - > - format = shm_format_for_depth(pixmap->drawable.depth); > - xwl_pixmap->buffer = wl_shm_pool_create_buffer(pool, 0, > - pixmap->drawable.width, > - pixmap->drawable.height, > - pixmap->devKind, format); > - > - wl_shm_pool_destroy(pool); > - > - return xwl_pixmap->buffer; > + return xwl_pixmap_get(pixmap)->buffer; > } > > Bool Hi Rui, the idea here looks fine to me. However, I've been wondering, surely there was a reason why it wasn't coded like this in the first place? Could you check if this patch causes Xwayland to create lots of wl_buffers it will never attach and commit to a wl_surface? If it does, that was probably the reason. If that is true, then one has to weigh between creating wl_buffers immediately vs. creating them only when actually needed for a wl_surface. Maybe Daniel knows? CC'ing also Olivier for his information. Thanks, pq
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