From: Leonardo Bras Date: Tue, 12 May 2020 21:45:35 +0000 (-0300) Subject: powerpc/crash: Use NMI context for printk when starting to crash X-Git-Tag: v5.8-rc1~132^2~37 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=af2876b501e42c3fb5174cac9dd02598436f0fdf;p=thirdparty%2Flinux.git 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: Michael Ellerman Signed-off-by: Leonardo Bras Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200512214533.93878-1-leobras.c@gmail.com --- diff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c index d488311efab1f..c9a889880214e 100644 --- a/arch/powerpc/kexec/crash.c +++ b/arch/powerpc/kexec/crash.c @@ -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.