Commit af2876b5 authored by Leonardo Bras's avatar Leonardo Bras Committed by Michael Ellerman
Browse files

powerpc/crash: Use NMI context for printk when starting to crash 



Currently, if printk lock (logbuf_lock) is held by other thread during
crash, there is a chance of deadlocking the crash on next printk, and
blocking a possibly desired kdump.

At the start of default_machine_crash_shutdown, make printk enter
NMI context, as it will use per-cpu buffers to store the message,
and avoid locking logbuf_lock.

Suggested-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: default avatarLeonardo Bras <leobras.c@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200512214533.93878-1-leobras.c@gmail.com
parent b6eca183

arch/powerpc/kexec/crash.c

+3 −0
Original line number Diff line number Diff line
@@ -311,6 +311,9 @@ void default_machine_crash_shutdown(struct pt_regs *regs) 
	unsigned int i;

	int (*old_handler)(struct pt_regs *regs);



	/* Avoid hardlocking with irresponsive CPU holding logbuf_lock */

	printk_nmi_enter();



	/*

	 * This function is only called after the system

	 * has panicked or is otherwise in a critical state.