----- On May 5, 2020, at 9:16 AM, Thomas Gleixner [email protected] wrote:
> From: Peter Zijlstra <[email protected]> > > A few exceptions (like #DB and #BP) can happen at any location in the code, > this then means that tracers should treat events from these exceptions as > NMI-like. The interrupted context could be holding locks with interrupts > disabled for instance. > > Similarly, #MC is an actual NMI-like exception. > > All of them use ist_enter() which only concerns itself with RCU, but does > not do any of the other setup that NMIs need. This means things like: > > printk() > raw_spin_lock_irq(&logbuf_lock); > <#DB/#BP/#MC> > printk() > raw_spin_lock_irq(&logbuf_lock); > > are entirely possible (well, not really since printk tries hard to > play nice, but the concept stands). > > So replace ist_enter() with nmi_enter(). Also observe that any nmi_enter() > caller must be both notrace and NOKPROBE, or in the noinstr text section. Are there similar issues with non-x86 architectures, or is this exception-behaves-like-an-interrupt issue specific to x86 ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
