lkml.org 
[lkml]   [2010]   [Nov]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Subject[PATCHSET RFC] ptrace,signal: sane interaction between ptrace and job control signals
Date
Hello,

This patchset is an attempt at cleaning up ptrace and signal
behaviors, especially the interaction between ptrace and group stop.
There are quite some number of problems in the area and the current
behavior is often racy, indeterministic and sometimes outright buggy.
This patchset aims to clean up the muddy stuff, and define and
implement a clear interaction between ptrace and job control.

This patchset contains the following fourteen patches.

0001-signal-fix-SIGCONT-notification-code.patch
0002-freezer-fix-a-race-during-freezing-of-TASK_STOPPED-t.patch
0003-freezer-remove-superflous-try_to_freeze-loop-in-do_s.patch
0004-signal-don-t-notify-parent-if-not-stopping-after-tra.patch
0005-signal-fix-premature-completion-of-group-stop-when-i.patch
0006-signal-use-GROUP_STOP_PENDING-to-avoid-stopping-mult.patch
0007-ptrace-add-why-to-ptrace_stop.patch
0008-ptrace-make-do_signal_stop-use-ptrace_stop-if-the-ta.patch
0009-ptrace-clean-transitions-between-TASK_STOPPED-and-TR.patch
0010-ptrace-don-t-consume-group-count-from-ptrace_stop.patch
0011-ptrace-make-group-stop-notification-reliable-against.patch
0012-ptrace-reorganize-__ptrace_unlink-and-ptrace_untrace.patch
0013-ptrace-make-SIGCONT-notification-reliable-against-pt.patch
0014-ptrace-remove-the-extra-wake_up_process-from-ptrace_.patch

0001-0002 are self-contained fixes. 0003-0004 are preparation
patches.

0005 fixes over-consumption of group_stop_count by ptraced tasks which
can lead to premature completion of group stop with some of the tasks
in the group still running.

0006 prevents a ptraced task from being stopped multiple times for the
same group stop instance.

0007-0009 updates the code such that a ptracee always enters and
leaves TASK_TRACED on its own. ptracer no longer changes tracee's
state underneath it; instead, it tells the tracee to enter the target
state. A TASK_TRACED task is guaranteed to be stopped inside
ptrace_stop() after executing the arch hooks while TASK_STOPPED task
is guaranteed to be stopped in do_signal_stop().

0010-0013 makes CLD_STOPPED/CONTINUED notification reliable with
intervening ptrace. Whether a ptracee owes an notification to its
parent is tracked and the real parent is notified accordingly on
detach.

0014 kills the unnecessary wake_up_process() which is wrong in so many
ways including the possibility of abruptly waking up a task in an
uninterruptible sleep. Now that ptrace / job control interaction is
cleaned up, this really should go.

After the patchset, the interaction between ptrace and job control is
defined as,

* Regardless of ptrace, job control signals control the process-wide
stopped state. A ptracee receives and handles job control signals
the same as before but no matter what ptrace does the global state
isn't affected.

* On ptrace detach, the task is put into the state which matches the
process-wide stopped state. If necessary, notification to the real
parent is reinstated.

Due to the implicit sending of SIGSTOP on PTRACE_ATTACH, ptrace
attach/detach are still not transparent w.r.t. job control but these
changes lay the base for (almost) transparent ptracing.

The branch is on top of 2.6.37-rc3 and available in the following git
branch,

git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git ptrace

and contains the following changes.

include/linux/sched.h | 11 +++
kernel/freezer.c | 9 ++-
kernel/power/process.c | 6 ++
kernel/ptrace.c | 105 +++++++++++++++++++++++++-----------
kernel/signal.c | 140 +++++++++++++++++++++++++++++++++----------------
5 files changed, 194 insertions(+), 77 deletions(-)
Thanks.

--
tejun


\
 
 \ /
  Last update: 2010-11-26 11:53    [from the cache]
©2003-2011 Jasper Spaans