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Bhat" Subject: [PATCH v5 02/45] percpu_rwlock: Introduce per-CPU variables for the reader and the writer To: tglx@linutronix.de, peterz@infradead.org, tj@kernel.org, oleg@redhat.com, paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au, mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org Date: Tue, 22 Jan 2013 13:03:32 +0530 Message-ID: <20130122073327.13822.96745.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> References: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13012207-8878-0000-0000-0000059D6F6D Cc: linux-arch@vger.kernel.org, linux@arm.linux.org.uk, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, fweisbec@gmail.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, xiaoguangrong@linux.vnet.ibm.com, rjw@sisk.pl, sbw@mit.edu, wangyun@linux.vnet.ibm.com, srivatsa.bhat@linux.vnet.ibm.com, netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" Per-CPU rwlocks ought to give better performance than global rwlocks. That is where the "per-CPU" component comes in. So introduce the necessary per-CPU variables that would be necessary at the reader and the writer sides, and add the support for dynamically initializing per-CPU rwlocks. These per-CPU variables will be used subsequently to implement the core algorithm behind per-CPU rwlocks. Cc: David Howells Signed-off-by: Srivatsa S. Bhat --- include/linux/percpu-rwlock.h | 4 ++++ lib/percpu-rwlock.c | 21 +++++++++++++++++++++ 2 files changed, 25 insertions(+) diff --git a/include/linux/percpu-rwlock.h b/include/linux/percpu-rwlock.h index 45620d0..cd5eab5 100644 --- a/include/linux/percpu-rwlock.h +++ b/include/linux/percpu-rwlock.h @@ -29,6 +29,8 @@ #include struct percpu_rwlock { + unsigned long __percpu *reader_refcnt; + bool __percpu *writer_signal; rwlock_t global_rwlock; }; @@ -41,6 +43,8 @@ extern void percpu_write_unlock(struct percpu_rwlock *); extern int __percpu_init_rwlock(struct percpu_rwlock *, const char *, struct lock_class_key *); +extern void percpu_free_rwlock(struct percpu_rwlock *); + #define percpu_init_rwlock(pcpu_rwlock) \ ({ static struct lock_class_key rwlock_key; \ __percpu_init_rwlock(pcpu_rwlock, #pcpu_rwlock, &rwlock_key); \ diff --git a/lib/percpu-rwlock.c b/lib/percpu-rwlock.c index af0c714..80dad93 100644 --- a/lib/percpu-rwlock.c +++ b/lib/percpu-rwlock.c @@ -31,6 +31,17 @@ int __percpu_init_rwlock(struct percpu_rwlock *pcpu_rwlock, const char *name, struct lock_class_key *rwlock_key) { + pcpu_rwlock->reader_refcnt = alloc_percpu(unsigned long); + if (unlikely(!pcpu_rwlock->reader_refcnt)) + return -ENOMEM; + + pcpu_rwlock->writer_signal = alloc_percpu(bool); + if (unlikely(!pcpu_rwlock->writer_signal)) { + free_percpu(pcpu_rwlock->reader_refcnt); + pcpu_rwlock->reader_refcnt = NULL; + return -ENOMEM; + } + /* ->global_rwlock represents the whole percpu_rwlock for lockdep */ #ifdef CONFIG_DEBUG_SPINLOCK __rwlock_init(&pcpu_rwlock->global_rwlock, name, rwlock_key); @@ -41,6 +52,16 @@ int __percpu_init_rwlock(struct percpu_rwlock *pcpu_rwlock, return 0; } +void percpu_free_rwlock(struct percpu_rwlock *pcpu_rwlock) +{ + free_percpu(pcpu_rwlock->reader_refcnt); + free_percpu(pcpu_rwlock->writer_signal); + + /* Catch use-after-free bugs */ + pcpu_rwlock->reader_refcnt = NULL; + pcpu_rwlock->writer_signal = NULL; +} + void percpu_read_lock(struct percpu_rwlock *pcpu_rwlock) { read_lock(&pcpu_rwlock->global_rwlock);