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From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Woody Suwalski <terraluna977@gmail.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linux PM <linux-pm@vger.kernel.org>
Subject: Re: kernel 5.2+: suspend freeze in VMware Player.
Date:   Mon, 25 Nov 2019 15:13:05 +0100
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On Saturday, November 23, 2019 11:51:19 PM CET Woody Suwalski wrote:
> Rafael, Thomas, this is the same VMware Player 15.2 freeze on suspend issue
> I have been discussing with you in August.
> 
> It has surfaced after Thomas Gleixner's change in kernel 5.2
> dfe0cf8b  x86/ioapic: Implement irq_get irqchip_state() callback
> 
> It is still with us in 5.4, 100% repeatable on a second suspend after a 
> reboot.
> 
> I have traced it down to the ioapic_irq_get_chip_state() function, where
> rentry.rr is stuck hi.
> 
> On the first suspend I can see that for IRQ9 the test exits with irr=0,
> trigger=1, but on second and consecutive suspends it is returning
> irr=1 trigger=1, so *state=1, and this results in a never-ending loop
> in __synchronize_hardirq(), because inprogress is always 1.
> 
> I have been usig a "fix" to timeout in __synchronize_hardirq() after
> 64 iterations, and that seems to work OK (no side-effects noticed),
> but of course is not addressing the underlying problem.
> 
> And the problem may be somewhere in VMware emulation code, returning bad 
> data?
> 
> Would you have ideas as to what should be the right setting for
> IRQ9 in VM environment?  Edge or level?
> And which part of code is reading the "hardware" state from VMware?
> 
> OTOH, current implementation is not really safe, as the wait loop should 

It is not clear to me the current implementation of what exactly you mean here.

> have a timeout, or else it may get stuck. Should I provide my safety-exit patch?

Thanks!