From: Matthew Wilcox <willy@infradead.org>
To: Michel Lespinasse <walken@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Laurent Dufour <ldufour@linux.ibm.com>,
Vlastimil Babka <vbabka@suse.cz>,
Liam Howlett <Liam.Howlett@oracle.com>,
Jerome Glisse <jglisse@redhat.com>,
Davidlohr Bueso <dave@stgolabs.net>,
David Rientjes <rientjes@google.com>,
Hugh Dickins <hughd@google.com>, Ying Han <yinghan@google.com>
Subject: Re: [PATCH 5/8] mmap locking API: convert nested write lock sites
Date: Thu, 26 Mar 2020 05:09:31 -0700 [thread overview]
Message-ID: <20200326120931.GF22483@bombadil.infradead.org> (raw)
In-Reply-To: <20200326070236.235835-6-walken@google.com>
On Thu, Mar 26, 2020 at 12:02:33AM -0700, Michel Lespinasse wrote:
> @@ -47,9 +48,9 @@ static inline void activate_mm(struct mm_struct *old, struct mm_struct *new)
> * when the new ->mm is used for the first time.
> */
> __switch_mm(&new->context.id);
> - down_write_nested(&new->mmap_sem, 1);
> + mmap_write_lock_nested(new, 1);
> uml_setup_stubs(new);
> - mmap_write_unlock(new);
> + mmap_write_unlock_nested(new);
This is a bit of an oddity. We don't usually have an unlock_nested()
variant (a quick grep finds only something complicated in reiserfs).
That's because it's legitimate to release locks in a different order from
the one they were acquired in (eg lock A, lock B, unlock A, unlock B), and
it's not clear whether "nested" would follow the lock (ie unlock_nested B)
or whether it would follow the code (ie unlock_nested A).
Does your future API require knowing the nested nature at the unlock
point? And if so, does it require it for A or B in the above scenario?
And how does it mix with lock A or B being of a different type (eg a
plain mutex or a spinlock)?
next prev parent reply other threads:[~2020-03-26 12:09 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-26 7:02 [PATCH 0/8] Add a new mmap locking API wrapping mmap_sem calls Michel Lespinasse
2020-03-26 7:02 ` [PATCH 1/8] mmap locking API: initial implementation as rwsem wrappers Michel Lespinasse
2020-03-26 17:56 ` Jason Gunthorpe
2020-03-26 18:06 ` Matthew Wilcox
2020-03-26 18:09 ` Matthew Wilcox
2020-03-26 22:09 ` Michel Lespinasse
2020-03-26 7:02 ` [PATCH 2/8] MMU notifier: use the new mmap locking API Michel Lespinasse
2020-03-26 7:02 ` [PATCH 3/8] mmap locking API: use coccinelle to convert mmap_sem rwsem call sites Michel Lespinasse
2020-03-27 0:01 ` kbuild test robot
2020-03-27 0:40 ` kbuild test robot
2020-03-26 7:02 ` [PATCH 4/8] mmap locking API: convert mmap_sem call sites missed by coccinelle Michel Lespinasse
2020-03-26 23:13 ` kbuild test robot
2020-03-26 23:27 ` kbuild test robot
2020-03-26 7:02 ` [PATCH 5/8] mmap locking API: convert nested write lock sites Michel Lespinasse
2020-03-26 12:09 ` Matthew Wilcox [this message]
2020-03-26 12:56 ` Michel Lespinasse
2020-03-26 7:02 ` [PATCH 6/8] mmap locking API: add mmap_read_release() and mmap_read_unlock_non_owner() Michel Lespinasse
2020-03-26 7:02 ` [PATCH 7/8] mmap locking API: add MMAP_LOCK_INITIALIZER Michel Lespinasse
2020-04-06 9:46 ` Laurent Dufour
2020-04-06 13:04 ` Michel Lespinasse
2020-03-26 7:02 ` [PATCH 8/8] mmap locking API: rename mmap_sem to mmap_lock Michel Lespinasse
2020-04-06 12:45 ` Laurent Dufour
2020-04-06 13:17 ` Michel Lespinasse
2020-04-06 16:03 ` Davidlohr Bueso
2020-03-26 7:13 ` [PATCH 0/8] Add a new mmap locking API wrapping mmap_sem calls Michel Lespinasse
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