From: "Paul E. McKenney" <paulmck@kernel.org>
To: Qian Cai <cai@lca.pw>
Cc: akpm@linux-foundation.org, John Hubbard <jhubbard@nvidia.com>,
elver@google.com, david@redhat.com, jack@suse.cz,
ira.weiny@intel.com, dan.j.williams@intel.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -next v2] mm: annotate a data race in page_zonenum()
Date: Wed, 19 Feb 2020 15:47:52 -0800 [thread overview]
Message-ID: <20200219234752.GS2935@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <1582149340.7365.103.camel@lca.pw>
On Wed, Feb 19, 2020 at 04:55:40PM -0500, Qian Cai wrote:
> Andrew, since you had picked the similar one which also depends
> on ASSERT_EXCLUSIVE_*, can you pick up this patch as well?
>
> On Thu, 2020-02-13 at 13:20 -0800, John Hubbard wrote:
> > On 2/13/20 10:38 AM, Qian Cai wrote:
> > > BUG: KCSAN: data-race in page_cpupid_xchg_last / put_page
> > >
> > > write (marked) to 0xfffffc0d48ec1a00 of 8 bytes by task 91442 on cpu 3:
> > > page_cpupid_xchg_last+0x51/0x80
> > > page_cpupid_xchg_last at mm/mmzone.c:109 (discriminator 11)
> > > wp_page_reuse+0x3e/0xc0
> > > wp_page_reuse at mm/memory.c:2453
> > > do_wp_page+0x472/0x7b0
> > > do_wp_page at mm/memory.c:2798
> > > __handle_mm_fault+0xcb0/0xd00
> > > handle_pte_fault at mm/memory.c:4049
> > > (inlined by) __handle_mm_fault at mm/memory.c:4163
> > > handle_mm_fault+0xfc/0x2f0
> > > handle_mm_fault at mm/memory.c:4200
> > > do_page_fault+0x263/0x6f9
> > > do_user_addr_fault at arch/x86/mm/fault.c:1465
> > > (inlined by) do_page_fault at arch/x86/mm/fault.c:1539
> > > page_fault+0x34/0x40
> > >
> > > read to 0xfffffc0d48ec1a00 of 8 bytes by task 94817 on cpu 69:
> > > put_page+0x15a/0x1f0
> > > page_zonenum at include/linux/mm.h:923
> > > (inlined by) is_zone_device_page at include/linux/mm.h:929
> > > (inlined by) page_is_devmap_managed at include/linux/mm.h:948
> > > (inlined by) put_page at include/linux/mm.h:1023
> > > wp_page_copy+0x571/0x930
> > > wp_page_copy at mm/memory.c:2615
> > > do_wp_page+0x107/0x7b0
> > > __handle_mm_fault+0xcb0/0xd00
> > > handle_mm_fault+0xfc/0x2f0
> > > do_page_fault+0x263/0x6f9
> > > page_fault+0x34/0x40
> > >
> > > Reported by Kernel Concurrency Sanitizer on:
> > > CPU: 69 PID: 94817 Comm: systemd-udevd Tainted: G W O L 5.5.0-next-20200204+ #6
> > > Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019
> > >
> > > A page never changes its zone number. The zone number happens to be
> > > stored in the same word as other bits which are modified, but the zone
> > > number bits will never be modified by any other write, so it can accept
> > > a reload of the zone bits after an intervening write and it don't need
> > > to use READ_ONCE(). Thus, annotate this data race using
> > > ASSERT_EXCLUSIVE_BITS() to also assert that there are no concurrent
> > > writes to it.
> > >
> > > Suggested-by: Marco Elver <elver@google.com>
> > > Signed-off-by: Qian Cai <cai@lca.pw>
> > > ---
> > >
> > > v2: use ASSERT_EXCLUSIVE_BITS().
> >
> >
> > Much cleaner, thanks to this new macro. You can add:
> >
> >
> > Reviewed-by: John Hubbard <jhubbard@nvidia.com>
It looks like Andrew already pulled this one in, but let me know if
he drops it for whatever reason.
Thanx, Paul
prev parent reply other threads:[~2020-02-19 23:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-13 18:38 [PATCH -next v2] mm: annotate a data race in page_zonenum() Qian Cai
2020-02-13 19:26 ` Paul E. McKenney
2020-02-14 14:30 ` Qian Cai
2020-02-14 16:16 ` Paul E. McKenney
2020-02-18 12:42 ` Qian Cai
2020-02-13 21:20 ` John Hubbard
2020-02-19 21:55 ` Qian Cai
2020-02-19 23:47 ` Paul E. McKenney [this message]
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