Re: [BUG] freeze Alpha ES40 SMP 2.4.4.ac3, another TCP/IP Problem ? ( was 2.4.4 kernel crash , possibly tcp related )

[Andrea Arcangeli <andrea@suse.de>]

On Thu, May 03, 2001 at 06:46:10PM +0200, Andrea Arcangeli wrote:
> as well. The only annoying thing is that UP kernel compiles seems not to
> boot but I hope that will be fixed soon too.

Ok I spotted and fixed that bug that forbidden my tree to boot with UP
compiles on alpha. The bug is that the SCHED_YIELD handling was broken
on alpha UP, this is the fix:

--- 2.4.5pre1aa1/arch/alpha/kernel/entry.S.~1~	Thu May  3 18:22:13 2001
+++ 2.4.5pre1aa1/arch/alpha/kernel/entry.S	Thu May  3 19:18:16 2001
@@ -709,16 +709,14 @@
 	br	restore_all
 .end entSys
 
-#ifdef CONFIG_SMP
-        .globl  ret_from_smp_fork
+        .globl  ret_from_fork
 .align 3
-.ent ret_from_smp_fork
-ret_from_smp_fork:
+.ent ret_from_fork
+ret_from_fork:
 	lda	$26,ret_from_sys_call
 	mov	$17,$16
 	jsr	$31,schedule_tail
-.end ret_from_smp_fork
-#endif /* CONFIG_SMP */
+.end ret_from_fork
 
 .align 3
 .ent reschedule
--- 2.4.5pre1aa1/arch/alpha/kernel/process.c.~1~	Thu May  3 18:22:09 2001
+++ 2.4.5pre1aa1/arch/alpha/kernel/process.c	Thu May  3 19:15:41 2001
@@ -306,7 +306,7 @@
 	    struct task_struct * p, struct pt_regs * regs)
 {
 	extern void ret_from_sys_call(void);
-	extern void ret_from_smp_fork(void);
+	extern void ret_from_fork(void);
 
 	struct pt_regs * childregs;
 	struct switch_stack * childstack, *stack;
@@ -325,11 +325,7 @@
 	stack = ((struct switch_stack *) regs) - 1;
 	childstack = ((struct switch_stack *) childregs) - 1;
 	*childstack = *stack;
-#ifdef CONFIG_SMP
-	childstack->r26 = (unsigned long) ret_from_smp_fork;
-#else
-	childstack->r26 = (unsigned long) ret_from_sys_call;
-#endif
+	childstack->r26 = (unsigned long) ret_from_fork;
 	p->thread.usp = usp;
 	p->thread.ksp = (unsigned long) childstack;
 	p->thread.pal_flags = 1;	/* set FEN, clear everything else */


(SCHED_YIELD of the previous task is cleared by __schedule_tail, it
wasn't cleared so a non running task had a SCHED_YIELD set and it was
deadlocking, this can explain many malfunction of UP alpha kernels)
I never noticed so far because I always compiled it SMP.

Andrea