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Commit 5cb4cc0d authored by Haren Myneni's avatar Haren Myneni Committed by Linus Torvalds
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[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: default avatarHaren Myneni <hbabu@us.ibm.com>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 0b2bfb4e

arch/ppc64/xmon/xmon.c

+3 −0
Original line number Diff line number Diff line
@@ -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);