From: Nicholas Piggin <npiggin@gmail.com>
To: peterz@infradead.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
Jens Axboe <axboe@kernel.dk>,
"David S. Miller" <davem@davemloft.net>,
linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 1/4] mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race
Date: Mon, 31 Aug 2020 11:25:39 +1000 [thread overview]
Message-ID: <1598836589.75k5wmftvn.astroid@bobo.none> (raw)
In-Reply-To: <20200828111525.GX1362448@hirez.programming.kicks-ass.net>
Excerpts from peterz@infradead.org's message of August 28, 2020 9:15 pm:
> On Fri, Aug 28, 2020 at 08:00:19PM +1000, Nicholas Piggin wrote:
>
>> Closing this race only requires interrupts to be disabled while ->mm
>> and ->active_mm are being switched, but the TLB problem requires also
>> holding interrupts off over activate_mm. Unfortunately not all archs
>> can do that yet, e.g., arm defers the switch if irqs are disabled and
>> expects finish_arch_post_lock_switch() to be called to complete the
>> flush; um takes a blocking lock in activate_mm().
>
> ARM at least has activate_mm() := switch_mm(), so it could be made to
> work.
>
Yeah, so long as that post_lock_switch switch did the right thing with
respect to its TLB flushing. It should do because arm doesn't seem to
check ->mm or ->active_mm (and if it was broken, the scheduler context
switch would be suspect too). I don't think the fix would be hard, just
that I don't have a good way to test it and qemu isn't great for testing
this kind of thing.
um too I think could probably defer that lock until after interrupts are
enabled again. I might throw a bunch of arch conversion patches over the
wall if this gets merged and try to move things along.
Thanks,
Nick
next prev parent reply other threads:[~2020-08-31 1:25 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-28 10:00 [PATCH 0/4] more mm switching vs TLB shootdown and lazy tlb Nicholas Piggin
2020-08-28 10:00 ` [PATCH 1/4] mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race Nicholas Piggin
2020-08-28 11:15 ` peterz
2020-08-31 1:25 ` Nicholas Piggin [this message]
2020-08-28 10:00 ` [PATCH 2/4] powerpc: select ARCH_WANT_IRQS_OFF_ACTIVATE_MM Nicholas Piggin
2020-08-28 10:00 ` [PATCH 3/4] sparc64: remove mm_cpumask clearing to fix kthread_use_mm race Nicholas Piggin
2020-08-28 10:00 ` [PATCH 4/4] powerpc/64s/radix: Fix mm_cpumask trimming race vs kthread_use_mm Nicholas Piggin
2020-09-01 12:00 ` Michael Ellerman
2020-09-02 9:48 ` Nicholas Piggin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1598836589.75k5wmftvn.astroid@bobo.none \
--to=npiggin@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=aneesh.kumar@linux.ibm.com \
--cc=axboe@kernel.dk \
--cc=davem@davemloft.net \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=peterz@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).