PERFORCE change 133972 for review

[Warner Losh]

http://perforce.freebsd.org/chv.cgi?CH=133972

Change 133972 by imp at imp_paco-paco on 2008/01/24 06:12:39

	Restore the 'oh no' checks just before userret(), per email
	from John Baldwin.  Don't understand his comments about ast()
	completely yet, so put the rest of his email in as a comment.
	I think need to track down where trap is called from and put
	some code in there...

Affected files ...

.. //depot/projects/mips2-jnpr/src/sys/mips/mips/trap.c#7 edit

Differences ...

==== //depot/projects/mips2-jnpr/src/sys/mips/mips/trap.c#7 (text+ko) ====

@@ -291,9 +291,7 @@
 
 static int emulate_unaligned_access(struct trapframe *frame);
 
-#ifdef WITNESS
 extern char *syscallnames[];
-#endif
 
 /*
  * Handle an exception.
@@ -799,6 +797,22 @@
 		 * of being done here under a special check for SYS_ptrace().
 		 */
 	done:
+		/*
+		 * Check for misbehavior.
+		 */
+		WITNESS_WARN(WARN_PANIC, NULL, "System call %s returning",
+		    (code >= 0 && code < SYS_MAXSYSCALL) ?
+		    syscallnames[code] : "???");
+		KASSERT(td->td_critnest == 0,
+		    ("System call %s returning in a critical section",
+			(code >= 0 && code < SYS_MAXSYSCALL) ?
+			syscallnames[code] : "???"));
+		KASSERT(td->td_locks == 0,
+		    ("System call %s returning with %d locks held",
+			(code >= 0 && code < SYS_MAXSYSCALL) ?
+			syscallnames[code] : "???",
+			td->td_locks));
+
 		userret(td, trapframe);
 
 #ifdef KTRACE
@@ -813,12 +827,48 @@
 		STOPEVENT(p, S_SCX, code);
 
 		PTRACESTOP_SC(p, td, S_PT_SCX);
+
 #ifdef GONE_IN_7
-		WITNESS_WARN(WARN_PANIC, NULL, "System call %s returning",
-		    (code >= 0 && code < SYS_MAXSYSCALL) ?
-		    syscallnames[code] : "???");
-		mtx_assert(&sched_lock, MA_NOTOWNED);
-		mtx_assert(&Giant, MA_NOTOWNED);
+		/*
+		 * XXX ast still need to happen
+		 *
+		 * Mail from jhb@:
+		 *
+		 * ast() is also still relevant in 7 as well.  What
+		 * normally happens is that you have the following in
+		 * assembly:
+		 * 
+		 * trap_entry:
+		 *	setup regs
+		 *	call trap
+		 *	jmp  exittrap
+		 *
+		 * syscall_entry:
+		 *	setup regs
+		 *	call syscall
+		 *	jmp  exittrap
+		 *
+		 * exittrap:
+		 *	get ready to return from trap
+		 *	disable interrupts
+		 *	if returning to kernel jmp kernel
+		 * asts:
+		 *	if no ASTs are pending jmp kernel
+		 *	enable interrupts
+		 *	call ast
+		 *	disable interrupts
+		 *	jmp asts
+		 * kernel:
+		 *	restore registers
+		 *	reti
+		 *
+		 * or some such.  You could do it in C if you wanted,
+		 * but the idea is you want to only return to userland
+		 * once you've verified you have no ASTs with
+		 * interrupts disabled.  If you get any AST's while
+		 * returning to userland it's due to SMP and you will
+		 * get an IPI that will post with 'reti' finishes.
+		 */
 		if (curthread->td_flags & (TDF_ASTPENDING|TDF_NEEDRESCHED)) {
 			ast(trapframe);
 		}