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From: Jason Gunthorpe <jgg@ziepe.ca>
To: linux-rdma@vger.kernel.org, linux-mm@kvack.org,
	Jerome Glisse <jglisse@redhat.com>,
	Ralph Campbell <rcampbell@nvidia.com>,
	John Hubbard <jhubbard@nvidia.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Subject: [RFC PATCH 06/11] mm/hmm: Remove duplicate condition test before wait_event_timeout
Date: Thu, 23 May 2019 12:34:31 -0300	[thread overview]
Message-ID: <20190523153436.19102-7-jgg@ziepe.ca> (raw)
In-Reply-To: <20190523153436.19102-1-jgg@ziepe.ca>

From: Jason Gunthorpe <jgg@mellanox.com>

The wait_event_timeout macro already tests the condition as its first
action, so there is no reason to open code another version of this, all
that does is skip the might_sleep() debugging in common cases, which is
not helpful.

Further, based on prior patches, we can no simplify the required condition
test:
 - If range is valid memory then so is range->hmm
 - If hmm_release() has run then range->valid is set to false
   at the same time as dead, so no reason to check both.
 - A valid hmm has a valid hmm->mm.

Also, add the READ_ONCE for range->valid as there is no lock held here.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
---
 include/linux/hmm.h | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 2a7346384ead13..7f3b751fcab1ce 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -216,17 +216,9 @@ static inline unsigned long hmm_range_page_size(const struct hmm_range *range)
 static inline bool hmm_range_wait_until_valid(struct hmm_range *range,
 					      unsigned long timeout)
 {
-	/* Check if mm is dead ? */
-	if (range->hmm == NULL || range->hmm->dead || range->hmm->mm == NULL) {
-		range->valid = false;
-		return false;
-	}
-	if (range->valid)
-		return true;
-	wait_event_timeout(range->hmm->wq, range->valid || range->hmm->dead,
+	wait_event_timeout(range->hmm->wq, range->valid,
 			   msecs_to_jiffies(timeout));
-	/* Return current valid status just in case we get lucky */
-	return range->valid;
+	return READ_ONCE(range->valid);
 }
 
 /*
-- 
2.21.0


  parent reply	other threads:[~2019-05-23 15:34 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-23 15:34 [RFC PATCH 00/11] mm/hmm: Various revisions from a locking/code review Jason Gunthorpe
2019-05-23 15:34 ` [RFC PATCH 01/11] mm/hmm: Fix use after free with struct hmm in the mmu notifiers Jason Gunthorpe
2019-06-06 23:54   ` Ira Weiny
2019-06-07 14:17     ` Jason Gunthorpe
2019-05-23 15:34 ` [RFC PATCH 02/11] mm/hmm: Use hmm_mirror not mm as an argument for hmm_register_range Jason Gunthorpe
2019-05-23 18:22   ` Christoph Hellwig
2019-05-23 15:34 ` [RFC PATCH 03/11] mm/hmm: Hold a mmgrab from hmm to mm Jason Gunthorpe
2019-05-23 15:34 ` [RFC PATCH 04/11] mm/hmm: Simplify hmm_get_or_create and make it reliable Jason Gunthorpe
2019-05-23 23:38   ` Ralph Campbell
2019-05-24  1:23     ` Jason Gunthorpe
2019-05-24 17:06       ` Ralph Campbell
2019-05-23 15:34 ` [RFC PATCH 05/11] mm/hmm: Improve locking around hmm->dead Jason Gunthorpe
2019-05-24 13:40   ` Jason Gunthorpe
2019-05-23 15:34 ` Jason Gunthorpe [this message]
2019-05-23 15:34 ` [RFC PATCH 07/11] mm/hmm: Delete hmm_mirror_mm_is_alive() Jason Gunthorpe
2019-05-23 15:34 ` [RFC PATCH 08/11] mm/hmm: Use lockdep instead of comments Jason Gunthorpe
2019-06-07 19:33   ` Souptick Joarder
2019-06-07 19:39     ` Jason Gunthorpe
2019-06-07 21:02       ` Souptick Joarder
2019-06-08  1:15         ` Jason Gunthorpe
2019-05-23 15:34 ` [RFC PATCH 09/11] mm/hmm: Remove racy protection against double-unregistration Jason Gunthorpe
2019-06-07 19:38   ` Souptick Joarder
2019-06-07 19:37     ` Jason Gunthorpe
2019-06-07 19:55       ` Souptick Joarder
2019-05-23 15:34 ` [RFC PATCH 10/11] mm/hmm: Poison hmm_range during unregister Jason Gunthorpe
2019-06-07 20:13   ` Souptick Joarder
2019-06-07 20:18     ` Jason Gunthorpe
2019-05-23 15:34 ` [RFC PATCH 11/11] mm/hmm: Do not use list*_rcu() for hmm->ranges Jason Gunthorpe
2019-06-07 20:22   ` Souptick Joarder
2019-05-23 19:04 ` [RFC PATCH 00/11] mm/hmm: Various revisions from a locking/code review John Hubbard
2019-05-23 19:37   ` Jason Gunthorpe
2019-05-23 20:59   ` Jerome Glisse
2019-05-24 13:35 ` Jason Gunthorpe
2019-05-24 14:36 ` Jason Gunthorpe
2019-05-24 16:49   ` Jerome Glisse
2019-05-24 16:59     ` Jason Gunthorpe
2019-05-24 17:01       ` Jerome Glisse
2019-05-24 17:52         ` Jason Gunthorpe
2019-05-24 18:03           ` Jerome Glisse
2019-05-24 18:32             ` Jason Gunthorpe
2019-05-24 18:46               ` Jerome Glisse
2019-05-24 22:09                 ` Jason Gunthorpe
2019-05-27 19:58                   ` Jason Gunthorpe
2019-05-24 17:47     ` Ralph Campbell
2019-05-24 17:51       ` Jerome Glisse

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