Re: [Xen-ia64-devel] [RFC][Patch] fix boot xen-ia64 on some ia64 platforms

[Akio Takebe]

Hi,

Thank you for comments.
Isaku Yamahata wrote:

On Tue, Apr 21, 2009 at 10:27:02AM +0900, Akio Takebe wrote:

Hi,

The following changeset broke booting xen-ia64 on some kinds of ia64 boxes.
http://xenbits.xensource.com/ext/ia64/xen-unstable.hg/rev/3fd8f9b34941

The tasklet_schedule call raise_softirq().
Because raise_softirq() use per_cpu, if we access per_cpu before cpu_init()
the behavior would be unexpected.

I make the following patch for this investigation.
It can boot xen-ia64 on the ia64 boxes.
I'm not sure why Tiger4 can boot the latest xen-ia64.
I didn't find a good-looking solution, what do you think about it?

Unfortunately, it happened to boot on my tiger4 so that I pushed out
the change set.
I Understood the issue. Looking into the boot sequence, it seems
to somewhat difficult to move down init_console() after cpu_init()
and remove all the printk() before cpu_init().
Hmm, it needs some consideration.

I also move some function after cpu_init().
But it failed to boot. So we may need such a early_printk().
I think we should not call tasklet_schedule() before softirq_init() at least on 
x86.
So how about the attached patch?

BTW, is there similar issue on ia64 linux case before?

No, I have not met.

Best Regards,

Akio Takebe

---
diff -r 8c806c66a597 xen/arch/ia64/xen/xensetup.c
--- a/xen/arch/ia64/xen/xensetup.c      Tue Apr 14 14:04:58 2009 +0900
+++ b/xen/arch/ia64/xen/xensetup.c      Tue Apr 21 13:42:26 2009 +0900
@@ -564,9 +564,9 @@ skip_move:

     end_boot_allocator();

+    late_setup_arch(&cmdline);
+
     softirq_init();
-
-    late_setup_arch(&cmdline);

     scheduler_init();
     idle_vcpu[0] = (struct vcpu*) ia64_r13;
diff -r 8c806c66a597 xen/common/softirq.c
--- a/xen/common/softirq.c      Tue Apr 14 14:04:58 2009 +0900
+++ b/xen/common/softirq.c      Tue Apr 21 13:42:26 2009 +0900
@@ -20,7 +20,7 @@ irq_cpustat_t irq_stat[NR_CPUS];
 irq_cpustat_t irq_stat[NR_CPUS];
 #endif

-static softirq_handler softirq_handlers[NR_SOFTIRQS];
+softirq_handler softirq_handlers[NR_SOFTIRQS];

 asmlinkage void do_softirq(void)
 {
diff -r 8c806c66a597 xen/drivers/char/console.c
--- a/xen/drivers/char/console.c        Tue Apr 14 14:04:58 2009 +0900
+++ b/xen/drivers/char/console.c        Tue Apr 21 13:42:26 2009 +0900
@@ -117,6 +117,8 @@ custom_param("loglvl", parse_loglvl);
 custom_param("loglvl", parse_loglvl);
 custom_param("guest_loglvl", parse_guest_loglvl);

+extern softirq_handler softirq_handlers[NR_SOFTIRQS];
+
 static atomic_t print_everything = ATOMIC_INIT(0);

 #define ___parse_loglvl(s, ps, lvlstr, lvlnum)          \
@@ -354,7 +356,10 @@ static long guest_console_write(XEN_GUES
         {
             for ( kptr = kbuf; *kptr != '\0'; kptr++ )
                 putchar_console_ring(*kptr);
-            tasklet_schedule(&notify_dom0_con_ring_tasklet);
+              if (softirq_handlers[TASKLET_SOFTIRQ])
+                tasklet_schedule(&notify_dom0_con_ring_tasklet);
+              else
+                send_guest_global_virq(dom0, VIRQ_CON_RING);
         }

         spin_unlock_irq(&console_lock);
@@ -435,7 +440,10 @@ static void __putstr(const char *str)
     {
         while ( (c = *str++) != '\0' )
             putchar_console_ring(c);
-        tasklet_schedule(&notify_dom0_con_ring_tasklet);
+        if (softirq_handlers[TASKLET_SOFTIRQ])
+            tasklet_schedule(&notify_dom0_con_ring_tasklet);
+       else
+            send_guest_global_virq(dom0, VIRQ_CON_RING);
     }
 }



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