[IA64] unwind did not work for processes born with CLONE_STOPPED

[IA64] unwind did not work for processes born with CLONE_STOPPED

[Kirill Korotaev]

[IA64] unwind did not work for processes born with CLONE_STOPPED

Minor problem for mainstream. Big problem for CPT, because all the
stopped/traced processes are born in this state, hence they cannot
be checkpointed again due to failing unwind.

The problem was identified as assumption in kernel unwind library
that top level frame is different of syscall frame. It is the case
unless process was born with CLONE_STOPPED.

Author: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-Off-By: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-Off-By: Kirill Korotaev <dev@sw.ru>

--- a/arch/ia64/kernel/unwind.c
+++ b/arch/ia64/kernel/unwind.c
@@ -60,6 +60,7 @@ #ifdef UNW_DEBUG
 #  define UNW_DEBUG_ON(n)	unw_debug_level >= n
    /* Do not code a printk level, not all debug lines end in newline */
 #  define UNW_DPRINT(n, ...)  if (UNW_DEBUG_ON(n)) printk(__VA_ARGS__)
+#  undef inline
 #  define inline
 #else /* !UNW_DEBUG */
 #  define UNW_DEBUG_ON(n)  0
@@ -1943,9 +1944,9 @@ EXPORT_SYMBOL(unw_unwind);
 int
 unw_unwind_to_user (struct unw_frame_info *info)
 {
-	unsigned long ip, sp, pr = 0;
+	unsigned long ip, sp, pr = info->pr;
 
-	while (unw_unwind(info) >= 0) {
+	do {
 		unw_get_sp(info, &sp);
 		if ((long)((unsigned long)info->task + IA64_STK_OFFSET - sp)
 		    < IA64_PT_REGS_SIZE) {
@@ -1963,7 +1964,7 @@ unw_unwind_to_user (struct unw_frame_inf
 				__FUNCTION__, ip);
 			return -1;
 		}
-	}
+	} while (unw_unwind(info) >= 0);
 	unw_get_ip(info, &ip);
 	UNW_DPRINT(0, "unwind.%s: failed to unwind to user-level (ip=0x%lx)\n",
 		   __FUNCTION__, ip);

Re: [IA64] unwind did not work for processes born with CLONE_STOPPED

[Christoph Hellwig]

On Mon, Mar 19, 2007 at 02:04:20PM +0300, Kirill Korotaev wrote:
> [IA64] unwind did not work for processes born with CLONE_STOPPED
> 
> Minor problem for mainstream. Big problem for CPT,

What is CPT?

Re: [IA64] unwind did not work for processes born with CLONE_STOPPED

[Kirill Korotaev]

Christoph Hellwig wrote:
> On Mon, Mar 19, 2007 at 02:04:20PM +0300, Kirill Korotaev wrote:
> 
>>[IA64] unwind did not work for processes born with CLONE_STOPPED
>>
>>Minor problem for mainstream. Big problem for CPT,
> 
> 
> What is CPT?

It is checkpointing/restore feature from OpenVZ.
Sorry for confusion in the comment.

Kirill