From: Marek Szyprowski <m.szyprowski@samsung.com>
To: Mel Gorman <mgorman@techsingularity.net>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Nicolas Saenz Julienne <nsaenzju@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Vlastimil Babka <vbabka@suse.cz>,
Michal Hocko <mhocko@kernel.org>, Hugh Dickins <hughd@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH 7/7] mm/page_alloc: Replace local_lock with normal spinlock
Date: Thu, 16 Jun 2022 00:48:55 +0200 [thread overview]
Message-ID: <e1c73640-3f29-bf57-b98d-84b1800cf4e3@samsung.com> (raw)
In-Reply-To: <20220613125622.18628-8-mgorman@techsingularity.net>
Hi Mel,
On 13.06.2022 14:56, Mel Gorman wrote:
> struct per_cpu_pages is no longer strictly local as PCP lists can be
> drained remotely using a lock for protection. While the use of local_lock
> works, it goes against the intent of local_lock which is for "pure
> CPU local concurrency control mechanisms and not suited for inter-CPU
> concurrency control" (Documentation/locking/locktypes.rst)
>
> local_lock protects against migration between when the percpu pointer is
> accessed and the pcp->lock acquired. The lock acquisition is a preemption
> point so in the worst case, a task could migrate to another NUMA node
> and accidentally allocate remote memory. The main requirement is to pin
> the task to a CPU that is suitable for PREEMPT_RT and !PREEMPT_RT.
>
> Replace local_lock with helpers that pin a task to a CPU, lookup the
> per-cpu structure and acquire the embedded lock. It's similar to local_lock
> without breaking the intent behind the API. It is not a complete API
> as only the parts needed for PCP-alloc are implemented but in theory,
> the generic helpers could be promoted to a general API if there was
> demand for an embedded lock within a per-cpu struct with a guarantee
> that the per-cpu structure locked matches the running CPU and cannot use
> get_cpu_var due to RT concerns. PCP requires these semantics to avoid
> accidentally allocating remote memory.
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
This patch landed in linux next-20220614 as commit 54bcdc6744e3
("mm/page_alloc: replace local_lock with normal spinlock").
Unfortunately it causes some serious issues when some kernel debugging
options (CONFIG_PROVE_LOCKING and CONFIG_DEBUG_ATOMIC_SLEEP) are
enabled. I've observed this on various ARM 64bit and 32bit boards.
In the logs I see lots of errors like:
BUG: sleeping function called from invalid context at
./include/linux/sched/mm.h:274
BUG: scheduling while atomic: systemd-udevd/288/0x00000002
BUG: sleeping function called from invalid context at mm/filemap.c:2647
however there are also a fatal ones like:
Unable to handle kernel paging request at virtual address 00000000017a87b4
The issues seems to be a bit random. Looks like memory trashing.
Reverting $subject on top of current linux-next fixes all those issues.
Let me know if how I can help debugging this.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
next prev parent reply other threads:[~2022-06-15 22:49 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-13 12:56 [PATCH v4 00/7] Drain remote per-cpu directly Mel Gorman
2022-06-13 12:56 ` [PATCH 1/7] mm/page_alloc: Add page->buddy_list and page->pcp_list Mel Gorman
2022-06-13 12:56 ` [PATCH 2/7] mm/page_alloc: Use only one PCP list for THP-sized allocations Mel Gorman
2022-06-13 12:56 ` [PATCH 3/7] mm/page_alloc: Split out buddy removal code from rmqueue into separate helper Mel Gorman
2022-06-13 12:56 ` [PATCH 4/7] mm/page_alloc: Remove mistaken page == NULL check in rmqueue Mel Gorman
2022-06-13 12:56 ` [PATCH 5/7] mm/page_alloc: Protect PCP lists with a spinlock Mel Gorman
2022-06-16 15:59 ` Vlastimil Babka
2022-06-13 12:56 ` [PATCH 6/7] mm/page_alloc: Remotely drain per-cpu lists Mel Gorman
2022-06-16 16:41 ` Vlastimil Babka
2022-06-13 12:56 ` [PATCH 7/7] mm/page_alloc: Replace local_lock with normal spinlock Mel Gorman
2022-06-15 22:43 ` Yu Zhao
[not found] ` <CGME20220615224855eucas1p1ea6d90c23ec9423dfe04b267f6dddd2a@eucas1p1.samsung.com>
2022-06-15 22:48 ` Marek Szyprowski [this message]
2022-06-15 23:04 ` Andrew Morton
2022-06-16 3:05 ` Yu Zhao
2022-06-17 7:55 ` Vlastimil Babka
2022-06-17 6:47 ` Marek Szyprowski
2022-06-21 9:21 ` Mel Gorman
2022-06-16 17:01 ` Vlastimil Babka
2022-06-16 21:07 ` Yu Zhao
2022-06-17 7:57 ` Vlastimil Babka
2022-06-21 9:27 ` Mel Gorman
2022-06-21 9:26 ` Mel Gorman
2022-06-17 9:39 ` Nicolas Saenz Julienne
2022-06-21 9:29 ` Mel Gorman
2022-06-21 9:31 ` Nicolas Saenz Julienne
2022-07-03 9:44 ` [mm/page_alloc] 2bd8eec68f: BUG:sleeping_function_called_from_invalid_context_at_mm/gup.c kernel test robot
2022-07-03 20:22 ` Andrew Morton
2022-07-05 13:51 ` Oliver Sang
2022-07-06 9:55 ` Mel Gorman
2022-07-06 11:53 ` Mel Gorman
2022-07-06 14:21 ` Oliver Sang
2022-07-06 14:52 ` Mel Gorman
2022-07-07 8:22 ` Oliver Sang
2022-07-06 14:25 ` Oliver Sang
2022-07-06 14:53 ` Mel Gorman
2022-07-07 21:55 ` Vlastimil Babka
2022-07-08 10:56 ` Mel Gorman
2022-07-12 5:04 ` Oliver Sang
2022-06-24 12:54 [PATCH v5 00/7] Drain remote per-cpu directly Mel Gorman
2022-06-24 12:54 ` [PATCH 7/7] mm/page_alloc: Replace local_lock with normal spinlock Mel Gorman
2022-06-24 18:59 ` Yu Zhao
2022-07-04 14:39 ` Vlastimil Babka
2022-07-04 16:33 ` Nicolas Saenz Julienne
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