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Re: handle_exit_race && PF_EXITING
- From: Thomas Gleixner <tglx at linutronix dot de>
- To: Oleg Nesterov <oleg at redhat dot com>
- Cc: Florian Weimer <fweimer at redhat dot com>, Shawn Landden <shawn at git dot icu>, libc-alpha at sourceware dot org, linux-api at vger dot kernel dot org, LKML <linux-kernel at vger dot kernel dot org>, Arnd Bergmann <arnd at arndb dot de>, Deepa Dinamani <deepa dot kernel at gmail dot com>, Andrew Morton <akpm at linux-foundation dot org>, Catalin Marinas <catalin dot marinas at arm dot com>, Keith Packard <keithp at keithp dot com>, Peter Zijlstra <peterz at infradead dot org>
- Date: Wed, 6 Nov 2019 18:42:13 +0100 (CET)
- Subject: Re: handle_exit_race && PF_EXITING
- References: <alpine.DEB.2.21.1911051053470.17054@nanos.tec.linutronix.de> <20191105152728.GA5666@redhat.com> <alpine.DEB.2.21.1911051800070.1869@nanos.tec.linutronix.de> <alpine.DEB.2.21.1911051851380.1869@nanos.tec.linutronix.de> <alpine.DEB.2.21.1911051920420.1869@nanos.tec.linutronix.de> <alpine.DEB.2.21.1911051959260.1869@nanos.tec.linutronix.de> <20191106085529.GA12575@redhat.com> <alpine.DEB.2.21.1911061028020.1869@nanos.tec.linutronix.de> <20191106103509.GB12575@redhat.com> <alpine.DEB.2.21.1911061154520.1869@nanos.tec.linutronix.de> <20191106121111.GC12575@redhat.com>
On Wed, 6 Nov 2019, Oleg Nesterov wrote:
>
> I think that (with or without this fix) handle_exit_race() logic needs
> cleanups, there is no reason for get_futex_value_locked(), we can drop
> ->pi_lock right after we see PF_EXITPIDONE. Lets discuss this later.
Which still is in atomic because the hash bucket lock is held, ergo
get_futex_value_locked() needs to stay for now.
So the only thing we could do is to reduce the pi_lock held section a bit.
Thanks,
tglx