[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>

diff --git a/arch/ppc64/xmon/xmon.c b/arch/ppc64/xmon/xmon.c
index 7f6e13a4b71eec0c23330aaca24dcc76aa6a5971..05539439e6bc0eef1b020f402a7b218b4f2841cf 100644 (file)
--- 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);