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From: Dave Chinner <david@fromorbit.com>
To: linux-xfs@vger.kernel.org
Subject: [PATCH 11/27] libxfs: add wrappers for kernel semaphores
Date: Thu, 15 Oct 2020 18:21:39 +1100
Message-ID: <20201015072155.1631135-12-david@fromorbit.com> (raw)
In-Reply-To: <20201015072155.1631135-1-david@fromorbit.com>

From: Dave Chinner <dchinner@redhat.com>

Implemented vi pthread mutexes.

On Linux, fast pthread mutexes don't actaully check which thread
owns the lock on unlock, so can be used in situations where the
unlock occurs in a different thread to the lock. This is
non-portable behaviour, so if other platforms are supported, this
may need to be converted to posix semaphores.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 include/Makefile     |  1 +
 include/libxfs.h     |  1 +
 include/sema.h       | 35 +++++++++++++++++++++++++++++++++++
 libxfs/libxfs_priv.h |  1 +
 4 files changed, 38 insertions(+)
 create mode 100644 include/sema.h

diff --git a/include/Makefile b/include/Makefile
index 98031e70fa0d..ce89d0237c19 100644
--- a/include/Makefile
+++ b/include/Makefile
@@ -17,6 +17,7 @@ LIBHFILES = libxfs.h \
 	kmem.h \
 	list.h \
 	parent.h \
+	sema.h \
 	spinlock.h \
 	xfs_inode.h \
 	xfs_log_recover.h \
diff --git a/include/libxfs.h b/include/libxfs.h
index d03ec8aeaf5c..923a376bd71a 100644
--- a/include/libxfs.h
+++ b/include/libxfs.h
@@ -20,6 +20,7 @@
 #include "atomic.h"
 #include "spinlock.h"
 #include "completion.h"
+#include "sema.h"
 
 #include "xfs_types.h"
 #include "xfs_fs.h"
diff --git a/include/sema.h b/include/sema.h
new file mode 100644
index 000000000000..bcccb156b0ea
--- /dev/null
+++ b/include/sema.h
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2019-20 RedHat, Inc.
+ * All Rights Reserved.
+ */
+#ifndef __LIBXFS_SEMA_H__
+#define __LIBXFS_SEMA_H__
+
+/*
+ * This implements kernel compatible semaphore _exclusion_ semantics. It does
+ * not implement counting semaphore behaviour.
+ *
+ * This makes use of the fact that fast pthread mutexes on Linux don't check
+ * that the unlocker is the same thread that locked the mutex, and hence can be
+ * unlocked in a different thread safely.
+ *
+ * If this needs to be portable or we require counting semaphore behaviour in
+ * libxfs code, this requires re-implementation based on posix semaphores.
+ */
+struct semaphore {
+	pthread_mutex_t		lock;
+};
+
+#define sema_init(l, nolock)		\
+do {					\
+	pthread_mutex_init(&(l)->lock, NULL);	\
+	if (!nolock)			\
+		pthread_mutex_lock(&(l)->lock);	\
+} while (0)
+
+#define down(l)			pthread_mutex_lock(&(l)->lock)
+#define down_trylock(l)		pthread_mutex_trylock(&(l)->lock)
+#define up(l)			pthread_mutex_unlock(&(l)->lock)
+
+#endif /* __LIBXFS_SEMA_H__ */
diff --git a/libxfs/libxfs_priv.h b/libxfs/libxfs_priv.h
index 5cbc4fe69732..7be3f7615fdd 100644
--- a/libxfs/libxfs_priv.h
+++ b/libxfs/libxfs_priv.h
@@ -50,6 +50,7 @@
 #include "atomic.h"
 #include "spinlock.h"
 #include "completion.h"
+#include "sema.h"
 
 #include "xfs_types.h"
 #include "xfs_arch.h"
-- 
2.28.0


  parent reply index

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-15  7:21 [PATCH 00/27] [RFC, WIP] xfsprogs: xfs_buf unification and AIO Dave Chinner
2020-10-15  7:21 ` [PATCH 01/27] xfsprogs: remove unused buffer tracing code Dave Chinner
2020-10-15  7:21 ` [PATCH 02/27] xfsprogs: remove unused IO_DEBUG functionality Dave Chinner
2020-11-16  2:31   ` Eric Sandeen
2020-10-15  7:21 ` [PATCH 03/27] libxfs: get rid of b_bcount from xfs_buf Dave Chinner
2020-11-23 19:53   ` Eric Sandeen
2020-10-15  7:21 ` [PATCH 04/27] libxfs: rename buftarg->dev to btdev Dave Chinner
2020-11-16  2:33   ` Eric Sandeen
2020-10-15  7:21 ` [PATCH 05/27] xfsprogs: get rid of ancient btree tracing fragments Dave Chinner
2020-11-16  2:35   ` Eric Sandeen
2020-10-15  7:21 ` [PATCH 06/27] xfsprogs: remove xfs_buf_t typedef Dave Chinner
2020-10-15 15:22   ` Darrick J. Wong
2020-10-15 20:54     ` Dave Chinner
2020-10-15  7:21 ` [PATCH 07/27] xfsprogs: introduce liburcu support Dave Chinner
2020-10-15  7:21 ` [PATCH 08/27] libxfs: add spinlock_t wrapper Dave Chinner
2020-10-15  7:21 ` [PATCH 09/27] atomic: convert to uatomic Dave Chinner
2020-10-15  7:21 ` [PATCH 10/27] libxfs: add kernel-compatible completion API Dave Chinner
2020-10-15 17:09   ` Darrick J. Wong
2020-10-19 22:21     ` Dave Chinner
2020-10-15  7:21 ` Dave Chinner [this message]
2020-10-15  7:21 ` [PATCH 12/27] xfsprogs: convert use-once buffer reads to uncached IO Dave Chinner
2020-10-15 17:12   ` Darrick J. Wong
2020-10-19 22:36     ` Dave Chinner
2020-10-15  7:21 ` [PATCH 13/27] libxfs: introduce userspace buftarg infrastructure Dave Chinner
2020-10-15  7:21 ` [PATCH 14/27] xfs: rename libxfs_buftarg_init to libxfs_open_devices() Dave Chinner
2020-10-15  7:21 ` [PATCH 15/27] libxfs: introduce userspace buftarg infrastructure Dave Chinner
2020-10-15 17:16   ` Darrick J. Wong
2020-10-15  7:21 ` [PATCH 16/27] libxfs: add a synchronous IO engine to the buftarg Dave Chinner
2020-10-15  7:21 ` [PATCH 17/27] xfsprogs: convert libxfs_readbufr to libxfs_buf_read_uncached Dave Chinner
2020-10-15  7:21 ` [PATCH 18/27] libxfs: convert libxfs_bwrite to buftarg IO Dave Chinner
2020-10-15  7:21 ` [PATCH 19/27] libxfs: add cache infrastructure to buftarg Dave Chinner
2020-10-15  7:21 ` [PATCH 20/27] libxfs: add internal lru to btcache Dave Chinner
2020-10-15  7:21 ` [PATCH 21/27] libxfs: Add kernel list_lru wrapper Dave Chinner
2020-10-15  7:21 ` [PATCH 22/27] libxfs: introduce new buffer cache infrastructure Dave Chinner
2020-10-15 17:46   ` Darrick J. Wong
2020-10-15  7:21 ` [PATCH 23/27] libxfs: use PSI information to detect memory pressure Dave Chinner
2020-10-15 17:56   ` Darrick J. Wong
2020-10-15 21:20     ` Dave Chinner
2020-10-15  7:21 ` [PATCH 24/27] libxfs: add a buftarg cache shrinker implementation Dave Chinner
2020-10-15 18:01   ` Darrick J. Wong
2020-10-15 21:33     ` Dave Chinner
2020-10-15  7:21 ` [PATCH 25/27] libxfs: switch buffer cache implementations Dave Chinner
2020-10-15  7:21 ` [PATCH 26/27] build: set platform_defs.h.in dependency correctly Dave Chinner
2020-10-15  7:21 ` [PATCH 27/27] libxfs: convert sync IO buftarg engine to AIO Dave Chinner
2020-10-15 18:26   ` Darrick J. Wong
2020-10-15 21:42     ` Dave Chinner
2020-10-15  7:29 ` [PATCH 00/27] [RFC, WIP] xfsprogs: xfs_buf unification and AIO Dave Chinner
2020-10-15 18:37 ` Darrick J. Wong
2020-10-15 22:35   ` Dave Chinner

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