| Summary: | xcb not re-enterant ... blocking desktop ... | ||
|---|---|---|---|
| Product: | XCB | Reporter: | Michael Meeks <michael.meeks> |
| Component: | Library | Assignee: | xcb mailing list dummy <xcb> |
| Status: | RESOLVED NOTOURBUG | QA Contact: | Xorg Project Team <xorg-team> |
| Severity: | critical | ||
| Priority: | medium | CC: | eich, mat, sndirsch |
| Version: | unspecified | ||
| Hardware: | Other | ||
| OS: | All | ||
| Whiteboard: | |||
| i915 platform: | i915 features: | ||
I would have thought that calling any Xlib function from a signal handler was unsafe... (In reply to comment #1) > I would have thought that calling any Xlib function from a signal handler was > unsafe... Absolutely - Xlib has never been async-signal safe. Very few library functions are (see the list in the POSIX/UNIX specs). 16:03 < jcristau> hrm. is XSync() really supposed to be ok to call from a
signal handler?
16:03 < jcristau> (bug 26728)
16:05 < ajax> jcristau: almost certainly not.
16:05 < jcristau> that's what i thought
16:05 < ajax> if you're in the middle of generating some other protocol, you'll
fuck up the protocol stream
16:05 < ajax> more generally, deadlocks ahoy.
closing as not our bug. don't do that.
Thanks for the prompt replies! :-) |
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Sooo ... I was pleased to actually catch this in the flesh, having seen similar symptoms on moblin and elsewhere; what happened ? I ran strace on evolution - and fetched some mail; this (it seems) caused evolution to either crash, or be suspended at an inconvenient time (via ptrace). strace itself was trying to write (perhaps a lot) of data to an xterm, which itself was trying to re-render via the window manager, whose compositing loop was stuck - waiting for the X server to finish it's dealings with evolution [ or so I infer ;-]. Even if this is not the flow problem above, the stack trace seems to suggest that in fact if a signal is caught during an xcb call that it is not re-enterancy safe [ typically we try to catch signals, and do nice things - like crash handlers in them ]. here are the obligatory traces. I strongly suspect we need to re-file this up-stream with xorg :-) Metacity: Thread 2 (Thread 0xb128fb70 (LWP 13433)): #0 0xffffe424 in __kernel_vsyscall () #1 0xb6addbeb in read () from /lib/libc.so.6 #2 0xb6d9141d in read (__nbytes=<value optimized out>, __buf=<value optimized out>, __fd=<value optimized out>) at /usr/include/bits/unistd.h:45 #3 child_watch_helper_thread (__nbytes=<value optimized out>, __buf=<value optimized out>, __fd=<value optimized out>) at gmain.c:3822 #4 0xb6dba9ef in g_thread_create_proxy (data=0x829ab00) at gthread.c:635 #5 0xb69e1725 in start_thread () from /lib/libpthread.so.0 #6 0xb6aee26e in clone () from /lib/libc.so.6 Thread 1 (Thread 0xb6830740 (LWP 9721)): #0 0xffffe424 in __kernel_vsyscall () #1 0xb6ae6f51 in select () from /lib/libc.so.6 #2 0xb6bb52dd in ?? () from /usr/lib/libxcb.so.1 #3 0xb6bb6cfa in xcb_wait_for_reply () from /usr/lib/libxcb.so.1 #4 0xb6c135d1 in _XReply () from /usr/lib/libX11.so.6 #5 0xb6bf1409 in XGrabPointer () from /usr/lib/libX11.so.6 #6 0x08060b67 in gdk_rectangle_intersect () at gdkrectangle.c:80 #7 0x08060e97 in gdk_rectangle_intersect () at gdkrectangle.c:80 #8 0x080709a4 in gdk_rectangle_intersect () at gdkrectangle.c:80 #9 0x0806d9bf in gdk_rectangle_intersect () at gdkrectangle.c:80 #10 0x08063a20 in gdk_rectangle_intersect () at gdkrectangle.c:80 #11 0x080ab11f in gdk_rectangle_intersect () at gdkrectangle.c:80 #12 0xb7270d36 in gdk_event_apply_filters (filters=<value optimized out>, event=<value optimized out>, xevent=<value optimized out>) at gdkevents-x11.c:351 #13 gdk_event_translate (filters=<value optimized out>, event=<value optimized out>, xevent=<value optimized out>) at gdkevents-x11.c:923 #14 0xb7272abf in _gdk_events_queue (display=0x80eb000 [GdkDisplayX11]) at gdkevents-x11.c:2306 #15 0xb7272eff in gdk_event_dispatch (source=0x80f2f88, callback=0, user_data=0x0) at gdkevents-x11.c:2367 #16 0xb6d90448 in g_main_dispatch (context=<value optimized out>) at gmain.c:1960 #17 IA__g_main_context_dispatch (context=<value optimized out>) at gmain.c:2513 #18 0xb6d93bf3 in g_main_context_iterate (context=0x80d6400, block=1, dispatch=1, self=0x80cd3e8) at gmain.c:2591 #19 0xb6d940ba in IA__g_main_loop_run (loop=0x80d6a00) at gmain.c:2799 #20 0x08071cac in gdk_rectangle_intersect () at gdkrectangle.c:80 #21 0xb6a30be5 in __libc_start_main () from /lib/libc.so.6 #22 0x08053bc1 in gdk_rectangle_intersect () at gdkrectangle.c:80 strace (not completing in 'write') #0 0xffffe424 in __kernel_vsyscall () #1 0xb761bc43 in __write_nocancel () from /lib/libc.so.6 #2 0xb75c0f5f in _IO_new_file_write () from /lib/libc.so.6 #3 0xb75c0c03 in new_do_write () from /lib/libc.so.6 #4 0xb75c0f06 in _IO_new_do_write () from /lib/libc.so.6 #5 0xb75c1ac0 in _IO_new_file_overflow () from /lib/libc.so.6 #6 0xb75c0d3d in _IO_new_file_xsputn () from /lib/libc.so.6 #7 0xb7595d63 in vfprintf () from /lib/libc.so.6 #8 0xb7640fce in __vfprintf_chk () from /lib/libc.so.6 #9 0x0804993d in geteuid () #10 0x08049992 in geteuid () #11 0x0804cc25 in geteuid () #12 0x0804c24d in geteuid () #13 0xb756ebe5 in __libc_start_main () from /lib/libc.so.6 #14 0x08049801 in geteuid () xterm (trying to catch up): (gdb) bt #0 0xffffe424 in __kernel_vsyscall () #1 0xb7348f1d in ___newselect_nocancel () from /lib/libc.so.6 #2 0xb723a2dd in ?? () from /usr/lib/libxcb.so.1 #3 0xb723aa2e in ?? () from /usr/lib/libxcb.so.1 #4 0xb723ab5f in ?? () from /usr/lib/libxcb.so.1 #5 0xb723acaf in xcb_flush () from /usr/lib/libxcb.so.1 #6 0xb7574a77 in _XSend () from /usr/lib/libX11.so.6 #7 0xb7574c00 in _XEventsQueued () from /usr/lib/libX11.so.6 #8 0xb755cb3f in XEventsQueued () from /usr/lib/libX11.so.6 #9 0xb746aab1 in XtAppPending () from /usr/lib/libXt.so.6 #10 0x08072cba in geteuid () #11 0x0805b820 in geteuid () #12 0x08061138 in geteuid () #13 0x0806125a in geteuid () #14 0x0806cb9e in geteuid () #15 0xb7292be5 in __libc_start_main () from /lib/libc.so.6 #16 0x0804d411 in geteuid () Xorg (quiescent ? or waiting for a sync call to complete?) (gdb) t a a bt Thread 1 (Thread 0xb72996f0 (LWP 9321)): #0 0xffffe424 in __kernel_vsyscall () #1 0xb7382f1d in ___newselect_nocancel () from /lib/libc.so.6 #2 0x08131a58 in WaitForSomething () #3 0x0808ce26 in Dispatch () #4 0x08071faa in main () Evolution (re-entering xcb_wait_for_reply - via a signal): (gdb) bt #0 0xffffe424 in __kernel_vsyscall () #1 0xb71663d5 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0 #2 0xb61b20b6 in ?? () from /usr/lib/libxcb.so.1 #3 0xb61b24e7 in ?? () from /usr/lib/libxcb.so.1 #4 0xb61b3cfa in xcb_wait_for_reply () from /usr/lib/libxcb.so.1 #5 0xb62105d1 in _XReply () from /usr/lib/libX11.so.6 #6 0xb62039c7 in XSync () from /usr/lib/libX11.so.6 #7 0xb6596268 in IA__gdk_flush () at gdkevents-x11.c:2554 #8 0xb55b7f1d in ?? () from /usr/lib/gtk-2.0/modules/libgnomebreakpad.so #9 <signal handler called> #10 0xffffe424 in __kernel_vsyscall () #11 0xb5ec5f51 in select () from /lib/libc.so.6 #12 0xb61b22dd in ?? () from /usr/lib/libxcb.so.1 #13 0xb61b3cfa in xcb_wait_for_reply () from /usr/lib/libxcb.so.1 #14 0xb62105d1 in _XReply () from /usr/lib/libX11.so.6 #15 0xb61fd73d in XQueryPointer () from /usr/lib/libX11.so.6 #16 0xb65ab33b in _gdk_windowing_window_at_pointer (display=0x808b000 [GdkDisplayX11], win_x=0xbf99cf1c, win_y=0xbf99cf18, mask=0x0, get_toplevel=0) at gdkwindow-x11.c:3247 #17 0xb655b55c in gdk_display_real_get_window_at_pointer (display=0x808b000 [GdkDisplayX11], win_x=0xbf99cf48, win_y=0xbf99cf44) at gdkdisplay.c:513 #18 0xb655bd8f in IA__gdk_display_get_window_at_pointer (display=0x808b000 [GdkDisplayX11], win_x=0xbf99cf70, win_y=0xbf99cf6c) at gdkdisplay.c:594 #19 0xb6844f8e in IA__gtk_tooltip_trigger_tooltip_query (display=0x808b000 [GdkDisplayX11]) at gtktooltip.c:438 #20 0xb5fb4a77 in IA__g_slist_foreach (list=0xa952260 = {...}, func=0xb6844f50 <IA__gtk_tooltip_trigger_tooltip_query>, user_data=0x0) at gslist.c:743 #21 0xb6886d12 in tooltip_query_idle (data=0x0) at gtkwidget.c:10678 #22 0xb655904b in gdk_threads_dispatch (data=0x9c1e2010) at gdk.c:506 #23 0xb5f93661 in g_idle_dispatch (source=0x107d4268, callback=0x1, user_data=0x9c1e2010) at gmain.c:4065 #24 0xb5f95448 in g_main_dispatch (context=<value optimized out>) at gmain.c:1960 #25 IA__g_main_context_dispatch (context=<value optimized out>) at gmain.c:2513 #26 0xb5f98bf3 in g_main_context_iterate (context=0x8094f50, block=1, dispatch=1, self=0x806b538) at gmain.c:2591 #27 0xb5f990ba in IA__g_main_loop_run (loop=0x80e2b50) at gmain.c:2799 #28 0xb6d1dfb3 in bonobo_main () at bonobo-main.c:311 #29 0x0805de3c in main (argc=1, argv=0x0) at main.c:732 HTH.