powerpc/xmon: Fix invocation inside lock region

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Currently xmon needs to get devtree_lock (through rtas_token()) during its
invocation (at crash time). If there is a crash while devtree_lock is being
held, then xmon tries to get the lock but spins forever and never get into
the interactive debugger, as in the following case:

	int *ptr = NULL;
	raw_spin_lock_irqsave(&devtree_lock, flags);
	*ptr = 0xdeadbeef;

This patch avoids calling rtas_token(), thus trying to get the same lock,
at crash time. This new mechanism proposes getting the token at
initialization time (xmon_init()) and just consuming it at crash time.

This would allow xmon to be possible invoked independent of devtree_lock
being held or not.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

...

This commit is contained in:

Breno Leitao 2018-11-08 15:12:42 -02:00 • committed by Michael Ellerman

parent 26598f2856

commit 8d4a862276

1 changed files with 14 additions and 4 deletions

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arch/powerpc/xmon/xmon.c

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