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SubjectRe: And another bug report for UML in latest Linux 2.6-BK repository.
Date
From
aia21@cam.ac.uk said:
> sleeping process 29410 got unexpected signal : 11
> I now have to press Ctrl+C to get back to my shell.

This one is slightly subtle, but I believe that it is fixed by the following
patch.

Jeff


Index: 2.6.9/arch/um/kernel/tt/process_kern.c
===================================================================
--- 2.6.9.orig/arch/um/kernel/tt/process_kern.c 2004-11-16 12:14:15.000000000 -0500
+++ 2.6.9/arch/um/kernel/tt/process_kern.c 2004-11-17 18:24:25.000000000 -0500
@@ -65,7 +65,8 @@
panic("write of switch_pipe failed, err = %d", -err);

reading = 1;
- if((from->exit_state == EXIT_ZOMBIE) || (from->exit_state == EXIT_DEAD))
+ if((from->exit_state == EXIT_ZOMBIE) ||
+ (from->exit_state == EXIT_DEAD))
os_kill_process(os_getpid(), 0);

err = os_read_file(from->thread.mode.tt.switch_pipe[0], &c, sizeof(c));
@@ -82,7 +83,7 @@
prev_sched = current->thread.prev_sched;
if((prev_sched->exit_state == EXIT_ZOMBIE) ||
(prev_sched->exit_state == EXIT_DEAD))
- os_kill_ptraced_process(prev_sched->thread.mode.tt.extern_pid, 1);
+ os_kill_process(prev_sched->thread.mode.tt.extern_pid, 1);

/* This works around a nasty race with 'jail'. If we are switching
* between two threads of a threaded app and the incoming process
Index: 2.6.9/arch/um/kernel/tt/tracer.c
===================================================================
--- 2.6.9.orig/arch/um/kernel/tt/tracer.c 2004-11-16 21:26:03.000000000 -0500
+++ 2.6.9/arch/um/kernel/tt/tracer.c 2004-11-17 18:21:47.000000000 -0500
@@ -271,10 +271,28 @@
#endif
else if(WIFSIGNALED(status)){
sig = WTERMSIG(status);
- if(sig != 9){
+ if(sig == SIGKILL){
+ /* This is to make sure that processes die
+ * immediately without becoming zombies on
+ * all hosts. Before 2.6.9, kill(pid, SIGKILL)
+ * was enough to make sure a process went away
+ * immediately. After 2.6.9, they don't run
+ * any more, but they remain as zombies. So,
+ * a PTRACE_CONT is necessary in order to put
+ * them in a normal run state so that they die.
+ * I do a PTRACE_KILL here for good measure.
+ * Might as well kill it by all available
+ * means. These calls will likely fail when
+ * they are not needed because the process has
+ * already disappeared. However, they don't
+ * hurt.
+ */
+ ptrace(PTRACE_KILL, pid, 0, 0);
+ ptrace(PTRACE_CONT, pid, 0, 0);
+ }
+ else
printf("Child %d exited with signal %d\n", pid,
sig);
- }
}
else if(WIFSTOPPED(status)){
proc_id = pid_to_processor_id(pid);
Index: 2.6.9/arch/um/os-Linux/process.c
===================================================================
--- 2.6.9.orig/arch/um/os-Linux/process.c 2004-11-16 12:14:15.000000000 -0500
+++ 2.6.9/arch/um/os-Linux/process.c 2004-11-17 18:27:52.000000000 -0500
@@ -95,9 +95,16 @@

}

+/* Kill off a ptraced child by all means available. kill it normally first,
+ * then PTRACE_KILL it, then PTRACE_CONT it in case it's in a run state from
+ * which it can't exit directly.
+ */
+
void os_kill_ptraced_process(int pid, int reap_child)
{
+ kill(pid, SIGKILL);
ptrace(PTRACE_KILL, pid);
+ ptrace(PTRACE_CONT, pid);
if(reap_child)
CATCH_EINTR(waitpid(pid, NULL, 0));
}
-
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