linux-kernel - Re: [PATCH v5 00/21] kprobes: Unify kretprobe trampoline handlers and make kretprobe lockless

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Date:   Wed, 2 Sep 2020 09:02:26 +0200
From:   peterz@...radead.org
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Eddy_Wu@...ndmicro.com, x86@...nel.org, davem@...emloft.net,
        rostedt@...dmis.org, naveen.n.rao@...ux.ibm.com,
        anil.s.keshavamurthy@...el.com, linux-arch@...r.kernel.org,
        cameron@...dycamel.com, oleg@...hat.com, will@...nel.org,
        paulmck@...nel.org
Subject: Re: [PATCH v5 00/21] kprobes: Unify kretprobe trampoline handlers
 and make kretprobe lockless

On Wed, Sep 02, 2020 at 09:37:39AM +0900, Masami Hiramatsu wrote:
> On Tue, 1 Sep 2020 21:08:08 +0200
> Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > On Sat, Aug 29, 2020 at 09:59:49PM +0900, Masami Hiramatsu wrote:
> > > Masami Hiramatsu (16):
> > >       kprobes: Add generic kretprobe trampoline handler
> > >       x86/kprobes: Use generic kretprobe trampoline handler
> > >       arm: kprobes: Use generic kretprobe trampoline handler
> > >       arm64: kprobes: Use generic kretprobe trampoline handler
> > >       arc: kprobes: Use generic kretprobe trampoline handler
> > >       csky: kprobes: Use generic kretprobe trampoline handler
> > >       ia64: kprobes: Use generic kretprobe trampoline handler
> > >       mips: kprobes: Use generic kretprobe trampoline handler
> > >       parisc: kprobes: Use generic kretprobe trampoline handler
> > >       powerpc: kprobes: Use generic kretprobe trampoline handler
> > >       s390: kprobes: Use generic kretprobe trampoline handler
> > >       sh: kprobes: Use generic kretprobe trampoline handler
> > >       sparc: kprobes: Use generic kretprobe trampoline handler
> > >       kprobes: Remove NMI context check
> > >       kprobes: Free kretprobe_instance with rcu callback
> > >       kprobes: Make local used functions static
> > > 
> > > Peter Zijlstra (5):
> > >       llist: Add nonatomic __llist_add() and __llist_dell_all()
> > >       kprobes: Remove kretprobe hash
> > >       asm-generic/atomic: Add try_cmpxchg() fallbacks
> > >       freelist: Lock less freelist
> > >       kprobes: Replace rp->free_instance with freelist
> > 
> > This looks good to me, do you want me to merge them through -tip? If so,
> > do we want to try and get them in this release still?
> 
> Yes, thanks. For the kretprobe missing issue, we will need the first half
> (up to "kprobes: Remove NMI context check"), so we can split the series
> if someone think the lockless is still immature.

Ok, but then lockdep will yell at you if you have that enabled and run
the unoptimized things.

> > Ingo, opinions? This basically fixes a regression cauesd by
> > 
> >   0d00449c7a28 ("x86: Replace ist_enter() with nmi_enter()")
> > 
> 
> Oops, I missed Ingo in CC. 

You had x86@, he'll have a copy :-)