Re: [PATCH][RFC] preemptive kernel: ptrace fix

[Robert Love]

On Sat, 2001-09-22 at 23:52, Robert Love wrote:
> However, doing an `strace strace whatever' (ie, stracing strace), it
> still enters a stopped state about 20% of the time (before the patch, it
> locked almost 100%).  I can't figure out why.  Comments?

I fixed it.  I am not overly sure why it fixes it, but the following
patch (on top of the previous) fixes all the ptrace problems I can find.

In auditing the code, I fixed another problem which I will explain...

I'll put out a final patch in a bit...

diff -urN linux-2.4.9-ac14-preempt/arch/i386/kernel/signal.c linux/arch/i386/kernel/signal.c
--- linux-2.4.9-ac14-preempt/arch/i386/kernel/signal.c	Sat Sep 22 23:20:41 2001
+++ linux/arch/i386/kernel/signal.c	Sun Sep 23 00:51:15 2001
@@ -611,9 +611,11 @@
 		if ((current->ptrace & PT_PTRACED) && signr != SIGKILL) {
 			/* Let the debugger run.  */
 			current->exit_code = signr;
+			ctx_sw_off();
 			current->state = TASK_STOPPED;
 			notify_parent(current, SIGCHLD);
 			schedule();
+			ctx_sw_on();
 
 			/* We're back.  Did the debugger cancel the sig?  */
 			if (!(signr = current->exit_code))
@@ -667,11 +669,13 @@
 				/* FALLTHRU */
 
 			case SIGSTOP:
+				ctx_sw_off();
 				current->state = TASK_STOPPED;
 				current->exit_code = signr;
 				if (!(current->p_pptr->sig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDSTOP))
 					notify_parent(current, SIGCHLD);
 				schedule();
+				ctx_sw_on();
 				continue;
 
 			case SIGQUIT: case SIGILL: case SIGTRAP:

-- 
Robert M. Love
rml at ufl.edu
rml at tech9.net