[PATCH] Xmon bug fix for soft-reset

For soft reset during system hang, got an error "CPU did not take
control" for some CPUs even though they responded to soft-reset (called
SystemReset, die and called debugger - xmon).   First these CPUs entered
into xmon by IPI callback and then got a soft-reset exception and
re-entered into xmon again. The first CPU which re-entered into xmon got
the output lock and made into xmon successfully without unlocking.
Hence, the next CPU(s) which re-entered into xmon try to acquire a lock
(get_output_lock). Therefore, we can not view state of those CPU(s).

[This is a simple, very low risk, obvious fix for an obvious bug, and
should go into 2.6.13.  -- paulus]

Signed-off-by: Haren Myneni <hbabu@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/ppc64/xmon/xmon.c b/arch/ppc64/xmon/xmon.c
index 7f6e13a4b71..05539439e6b 100644
--- a/arch/ppc64/xmon/xmon.c
+++ b/arch/ppc64/xmon/xmon.c
@@ -329,13 +329,16 @@ int xmon_core(struct pt_regs *regs, int fromipi)
                 printf("cpu 0x%x: Exception %lx %s in xmon, "
                        "returning to main loop\n",
                        cpu, regs->trap, getvecname(TRAP(regs)));
+                release_output_lock();
                 longjmp(xmon_fault_jmp[cpu], 1);
         }
 
         if (setjmp(recurse_jmp) != 0) {
                 if (!in_xmon || !xmon_gate) {
+                        get_output_lock();
                         printf("xmon: WARNING: bad recursive fault "
                                "on cpu 0x%x\n", cpu);
+                        release_output_lock();
                         goto waiting;
                 }
                 secondary = !(xmon_taken && cpu == xmon_owner);