linux-kernel - Re: [patch V2 07/15] powerpc/ps3: Convert half completion to rcuwait

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Message-ID: <20200319100459.GA18506@infradead.org>
Date:   Thu, 19 Mar 2020 03:04:59 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-pci@...r.kernel.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        netdev@...r.kernel.org, Joel Fernandes <joel@...lfernandes.org>,
        Will Deacon <will@...nel.org>, Ingo Molnar <mingo@...nel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Logan Gunthorpe <logang@...tatee.com>,
        Arnd Bergmann <arnd@...db.de>, linuxppc-dev@...ts.ozlabs.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Kurt Schwemmer <kurt.schwemmer@...rosemi.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-wireless@...r.kernel.org,
        Oleg Nesterov <oleg@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [patch V2 07/15] powerpc/ps3: Convert half completion to rcuwait

On Wed, Mar 18, 2020 at 09:43:09PM +0100, Thomas Gleixner wrote:
> The PS3 notification interrupt and kthread use a hacked up completion to
> communicate. Since we're wanting to change the completion implementation and
> this is abuse anyway, replace it with a simple rcuwait since there is only ever
> the one waiter.
> 
> AFAICT the kthread uses TASK_INTERRUPTIBLE to not increase loadavg, kthreads
> cannot receive signals by default and this one doesn't look different. Use
> TASK_IDLE instead.

I think the right fix here is to jut convert the thing to a threaded
interrupt handler and kill off the stupid kthread.

But I wonder how alive the whole PS3 support is to start with..