[Bug 930004] Re: update-manager assert failure: python: ../../src/xcb_io.c:273: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.

[Bryce Harrington]

The error message "Unknown sequence number while processing queue"
occurs in a chunk of text that has this big fat warning in front of it,
about threading safety in client code:

/* Thread-safety rules:
 *
 * At most one thread can be reading from XCB's event queue at a time.
 * If you are not the current event-reading thread and you need to find
 * out if an event is available, you must wait.
 *
 * The same rule applies for reading replies.
 *
 * A single thread cannot be both the the event-reading and the
 * reply-reading thread at the same time.
 *
 * We always look at both the current event and the first pending reply
 * to decide which to process next.
 *
 * We always process all responses in sequence-number order, which may
 * mean waiting for another thread (either the event_waiter or the
 * reply_waiter) to handle an earlier response before we can process or
 * return a later one. If so, we wait on the corresponding condition
 * variable for that thread to process the response and wake us up.
 */

This seems to suggest perhaps this client application could have some
faulty logic in its thread handling as relating to the xcb calls?


** Description changed:

  Occurred when updating.
+ 
+ [xcb] Unknown sequence number while processing queue
+ [xcb] Most likely this is a multi-threaded client and XInitThreads has not been called
+ [xcb] Aborting, sorry about that.
+ python: ../../src/xcb_io.c:273: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.
  
  ProblemType: Crash
  DistroRelease: Ubuntu 12.04
  Package: update-manager 1:0.156.4
  ProcVersionSignature: Ubuntu 3.2.0-15.24-generic 3.2.5
  Uname: Linux 3.2.0-15-generic x86_64
  ApportVersion: 1.91-0ubuntu1
  Architecture: amd64
  AssertionMessage: python: ../../src/xcb_io.c:273: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.
  Date: Thu Feb  9 23:36:59 2012
  DuplicateOf: https://bugs.launchpad.net/bugs/926238
  ExecutablePath: /usr/bin/update-manager
  GsettingsChanges:
-  com.ubuntu.update-manager first-run false
-  com.ubuntu.update-manager launch-time 1327193820
-  com.ubuntu.update-manager show-details true
-  com.ubuntu.update-manager window-height 600
-  com.ubuntu.update-manager window-width 600
+  com.ubuntu.update-manager first-run false
+  com.ubuntu.update-manager launch-time 1327193820
+  com.ubuntu.update-manager show-details true
+  com.ubuntu.update-manager window-height 600
+  com.ubuntu.update-manager window-width 600
  InterpreterPath: /usr/bin/python2.7
  PackageArchitecture: all
  ProcCmdline: /usr/bin/python /usr/bin/update-manager --dist-upgrade
  ProcEnviron:
-  PATH=(custom, no user)
-  LANG=en_US.UTF-8
-  SHELL=/bin/bash
+  PATH=(custom, no user)
+  LANG=en_US.UTF-8
+  SHELL=/bin/bash
  Signal: 6
  SourcePackage: update-manager
  StacktraceTop:
-  __assert_fail_base (fmt=<optimized out>, assertion=0x7f20d7ceead8 "!xcb_xlib_threads_sequence_lost", file=0x7f20d7ceed92 "../../src/xcb_io.c", line=<optimized out>, function=<optimized out>) at assert.c:94
-  __GI___assert_fail (assertion=0x7f20d7ceead8 "!xcb_xlib_threads_sequence_lost", file=0x7f20d7ceed92 "../../src/xcb_io.c", line=273, function=0x7f20d7ceeeb8 "poll_for_event") at assert.c:103
-  ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
-  ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
-  _XEventsQueued () from /usr/lib/x86_64-linux-gnu/libX11.so.6
+  __assert_fail_base (fmt=<optimized out>, assertion=0x7f20d7ceead8 "!xcb_xlib_threads_sequence_lost", file=0x7f20d7ceed92 "../../src/xcb_io.c", line=<optimized out>, function=<optimized out>) at assert.c:94
+  __GI___assert_fail (assertion=0x7f20d7ceead8 "!xcb_xlib_threads_sequence_lost", file=0x7f20d7ceed92 "../../src/xcb_io.c", line=273, function=0x7f20d7ceeeb8 "poll_for_event") at assert.c:103
+  ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
+  ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
+  _XEventsQueued () from /usr/lib/x86_64-linux-gnu/libX11.so.6
  Title: update-manager assert failure: python: ../../src/xcb_io.c:273: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.
  UpgradeStatus: Upgraded to precise on 2012-02-10 (0 days ago)
  UserGroups:

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https://bugs.launchpad.net/bugs/930004

Title:
  update-manager assert failure: python: ../../src/xcb_io.c:273:
  poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.

Status in “update-manager” package in Ubuntu:
  Confirmed

Bug description:
  Occurred when updating.

  [xcb] Unknown sequence number while processing queue
  [xcb] Most likely this is a multi-threaded client and XInitThreads has not been called
  [xcb] Aborting, sorry about that.
  python: ../../src/xcb_io.c:273: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.

  ProblemType: Crash
  DistroRelease: Ubuntu 12.04
  Package: update-manager 1:0.156.4
  ProcVersionSignature: Ubuntu 3.2.0-15.24-generic 3.2.5
  Uname: Linux 3.2.0-15-generic x86_64
  ApportVersion: 1.91-0ubuntu1
  Architecture: amd64
  AssertionMessage: python: ../../src/xcb_io.c:273: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.
  Date: Thu Feb  9 23:36:59 2012
  DuplicateOf: https://bugs.launchpad.net/bugs/926238
  ExecutablePath: /usr/bin/update-manager
  GsettingsChanges:
   com.ubuntu.update-manager first-run false
   com.ubuntu.update-manager launch-time 1327193820
   com.ubuntu.update-manager show-details true
   com.ubuntu.update-manager window-height 600
   com.ubuntu.update-manager window-width 600
  InterpreterPath: /usr/bin/python2.7
  PackageArchitecture: all
  ProcCmdline: /usr/bin/python /usr/bin/update-manager --dist-upgrade
  ProcEnviron:
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  Signal: 6
  SourcePackage: update-manager
  StacktraceTop:
   __assert_fail_base (fmt=<optimized out>, assertion=0x7f20d7ceead8 "!xcb_xlib_threads_sequence_lost", file=0x7f20d7ceed92 "../../src/xcb_io.c", line=<optimized out>, function=<optimized out>) at assert.c:94
   __GI___assert_fail (assertion=0x7f20d7ceead8 "!xcb_xlib_threads_sequence_lost", file=0x7f20d7ceed92 "../../src/xcb_io.c", line=273, function=0x7f20d7ceeeb8 "poll_for_event") at assert.c:103
   ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
   ?? () from /usr/lib/x86_64-linux-gnu/libX11.so.6
   _XEventsQueued () from /usr/lib/x86_64-linux-gnu/libX11.so.6
  Title: update-manager assert failure: python: ../../src/xcb_io.c:273: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.
  UpgradeStatus: Upgraded to precise on 2012-02-10 (0 days ago)
  UserGroups:

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