On Mon, Mar 29, 2021 at 11:23:45AM +0100, Daniel Thompson wrote: > On Sat, Mar 27, 2021 at 07:25:28PM -0400, Waiman Long wrote: > > The sched_debug_lock was used only in print_cpu(). The > > print_cpu() function has two callers - sched_debug_show() and > > sysrq_sched_debug_show(). Both of them are invoked by user action > > (sched_debug file and sysrq-t). As print_cpu() won't be called from > > interrupt context at all, there is no point in disabling IRQ when > > acquiring sched_debug_lock. > > This looks like it introduces a deadlock risk if sysrq-t triggers from an > interrupt context. Has the behaviour of sysrq changed recently or will > tools like MAGIC_SYSRQ_SERIAL still trigger from interrupt context?
Yeah, sysrq-t is very often interrupt context. The patch is clearly bogus.
