[PATCH] Hang when recursing in _cairo_scaled_font_reset_cache()
Hans Petter Jansson <[email protected]>
| Newsgroups | gmane.comp.lib.cairo |
|---|---|
| Message-ID | <[email protected]> |
Hi! I submitted a patch in bug 93891 [1] some time ago, and I wonder if someone on this list had a few spare moments to review it. The patch fixes a potential hang affecting client applications (observed with Evince). I'm attaching the same patch here for convenience. [1] https://bugs.freedesktop.org/show_bug.cgi?id=93891 -- Hans Petter -- cairo mailing list [email protected] https://lists.cairographics.org/mailman/listinfo/cairo
0001-scaled-font-Fix-deadlock-when-recursing-in-_cairo_sc.patch
(text/x-patch, 2.4 KB)
From 8a6de4f53fb0cf8b8af654c18eadc31ed3a9525e Mon Sep 17 00:00:00 2001 From: Hans Petter Jansson <[email protected]> Date: Wed, 27 Jan 2016 12:55:01 -0600 Subject: [PATCH] scaled-font: Fix deadlock when recursing in _cairo_scaled_font_reset_cache() The destruction of a scaled font could indirectly trigger the destruction of a second scaled font, causing the global cache to be locked twice in the same thread. This is solved by unlinking the font's glyph pages while holding the global lock, then releasing the lock before destruction takes place. Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=93891 --- src/cairo-scaled-font.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/src/cairo-scaled-font.c b/src/cairo-scaled-font.c index ac80c97..a22b36e 100644 --- a/src/cairo-scaled-font.c +++ b/src/cairo-scaled-font.c @@ -818,23 +818,35 @@ _cairo_scaled_font_thaw_cache (cairo_scaled_font_t *scaled_font) void _cairo_scaled_font_reset_cache (cairo_scaled_font_t *scaled_font) { + cairo_scaled_glyph_page_t *page; + CAIRO_MUTEX_LOCK (scaled_font->mutex); assert (! scaled_font->cache_frozen); assert (! scaled_font->global_cache_frozen); CAIRO_MUTEX_LOCK (_cairo_scaled_glyph_page_cache_mutex); - while (! cairo_list_is_empty (&scaled_font->glyph_pages)) { - cairo_scaled_glyph_page_t *page = - cairo_list_first_entry (&scaled_font->glyph_pages, - cairo_scaled_glyph_page_t, - link); + cairo_list_foreach_entry (page, + cairo_scaled_glyph_page_t, + &scaled_font->glyph_pages, + link) { cairo_scaled_glyph_page_cache.size -= page->cache_entry.size; _cairo_hash_table_remove (cairo_scaled_glyph_page_cache.hash_table, (cairo_hash_entry_t *) &page->cache_entry); + } + CAIRO_MUTEX_UNLOCK (_cairo_scaled_glyph_page_cache_mutex); + + /* Destroy scaled_font's pages while holding its lock only, and not the + * global page cache lock. The destructor can cause us to recurse and + * end up back here for a different scaled_font. */ + + while (! cairo_list_is_empty (&scaled_font->glyph_pages)) { + page = cairo_list_first_entry (&scaled_font->glyph_pages, + cairo_scaled_glyph_page_t, + link); _cairo_scaled_glyph_page_destroy (scaled_font, page); } - CAIRO_MUTEX_UNLOCK (_cairo_scaled_glyph_page_cache_mutex); + CAIRO_MUTEX_UNLOCK (scaled_font->mutex); } -- 1.8.4.5