[PATCH v12 22/22] selftests/vm: Fix deadlock in protection_keys.c

[Dave Hansen]

On 02/21/2018 05:55 PM, Ram Pai wrote:
> From: Thiago Jung Bauermann <bauerman at linux.vnet.ibm.com>
> 
> The sig_chld() handler calls dprintf2() taking care of setting
> dprint_in_signal so that sigsafe_printf() won't call printf().
> Unfortunately, this precaution is is negated by dprintf_level(), which
> has a call to fflush().
> 
> This function acquires a lock, which means that if the signal interrupts an
> ongoing fflush() the process will deadlock. At least on powerpc this is
> easy to trigger, resulting in the following backtrace when attaching to the
> frozen process:

Ugh, yeah, I've run into this too.

Acked-by: Dave Hansen <dave.hansen at intel.com>