summaryrefslogtreecommitdiffstats
path: root/kernel/ptrace.c
diff options
context:
space:
mode:
authorOleg Nesterov <oleg@redhat.com>2011-04-01 20:12:38 +0200
committerTejun Heo <tj@kernel.org>2011-04-04 02:11:05 +0200
commitee77f075921730b2b465880f9fd4367003bdab39 (patch)
treedfae10b9718b79650477f912de148c903bc1bbd0 /kernel/ptrace.c
parent780006eac2fe7f4d2582da16a096e5a44c4767ff (diff)
downloadop-kernel-dev-ee77f075921730b2b465880f9fd4367003bdab39.zip
op-kernel-dev-ee77f075921730b2b465880f9fd4367003bdab39.tar.gz
signal: Turn SIGNAL_STOP_DEQUEUED into GROUP_STOP_DEQUEUED
This patch moves SIGNAL_STOP_DEQUEUED from signal_struct->flags to task_struct->group_stop, and thus makes it per-thread. Like SIGNAL_STOP_DEQUEUED, GROUP_STOP_DEQUEUED can be false-positive after return from get_signal_to_deliver(), this is fine. The only purpose of this bit is: we can drop ->siglock after __dequeue_signal() returns the sig_kernel_stop() signal and before we call do_signal_stop(), in this case we must not miss SIGCONT if it comes in between. But, unlike SIGNAL_STOP_DEQUEUED, GROUP_STOP_DEQUEUED can not be false-positive in do_signal_stop() if multiple threads dequeue the sig_kernel_stop() signal at the same time. Consider two threads T1 and T2, SIGTTIN has a hanlder. - T1 dequeues SIGTSTP and sets SIGNAL_STOP_DEQUEUED, then it drops ->siglock - SIGCONT comes and clears SIGNAL_STOP_DEQUEUED, SIGTSTP should be cancelled. - T2 dequeues SIGTTIN and sets SIGNAL_STOP_DEQUEUED again. Since we have a handler we should not stop, T2 returns to usermode to run the handler. - T1 continues, calls do_signal_stop() and wrongly starts the group stop because SIGNAL_STOP_DEQUEUED was restored in between. With or without this change: - we need to do something with ptrace_signal() which can return SIGSTOP, but this needs another discussion - SIGSTOP can be lost if it races with the mt exec, will be fixed later. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/ptrace.c')
0 files changed, 0 insertions, 0 deletions
OpenPOWER on IntegriCloud