From 1791f881435fab951939ad700e947b66c062e083 Mon Sep 17 00:00:00 2001 From: Richard Cochran Date: Wed, 30 Mar 2011 15:24:21 +0200 Subject: [PATCH 1/2] posix clocks: Replace mutex with reader/writer semaphore A dynamic posix clock is protected from asynchronous removal by a mutex. However, using a mutex has the unwanted effect that a long running clock operation in one process will unnecessarily block other processes. For example, one process might call read() to get an external time stamp coming in at one pulse per second. A second process calling clock_gettime would have to wait for almost a whole second. This patch fixes the issue by using a reader/writer semaphore instead of a mutex. Signed-off-by: Richard Cochran Cc: John Stultz Link: http://lkml.kernel.org/r/%3C20110330132421.GA31771%40riccoc20.at.omicron.at%3E Signed-off-by: Thomas Gleixner --- include/linux/posix-clock.h | 5 +++-- kernel/time/posix-clock.c | 24 +++++++++--------------- 2 files changed, 12 insertions(+), 17 deletions(-) diff --git a/include/linux/posix-clock.h b/include/linux/posix-clock.h index 369e19d3750..7f1183dcd11 100644 --- a/include/linux/posix-clock.h +++ b/include/linux/posix-clock.h @@ -24,6 +24,7 @@ #include #include #include +#include struct posix_clock; @@ -104,7 +105,7 @@ struct posix_clock_operations { * @ops: Functional interface to the clock * @cdev: Character device instance for this clock * @kref: Reference count. - * @mutex: Protects the 'zombie' field from concurrent access. + * @rwsem: Protects the 'zombie' field from concurrent access. * @zombie: If 'zombie' is true, then the hardware has disappeared. * @release: A function to free the structure when the reference count reaches * zero. May be NULL if structure is statically allocated. @@ -117,7 +118,7 @@ struct posix_clock { struct posix_clock_operations ops; struct cdev cdev; struct kref kref; - struct mutex mutex; + struct rw_semaphore rwsem; bool zombie; void (*release)(struct posix_clock *clk); }; diff --git a/kernel/time/posix-clock.c b/kernel/time/posix-clock.c index 25028dd4fa1..c340ca658f3 100644 --- a/kernel/time/posix-clock.c +++ b/kernel/time/posix-clock.c @@ -19,7 +19,6 @@ */ #include #include -#include #include #include #include @@ -34,19 +33,19 @@ static struct posix_clock *get_posix_clock(struct file *fp) { struct posix_clock *clk = fp->private_data; - mutex_lock(&clk->mutex); + down_read(&clk->rwsem); if (!clk->zombie) return clk; - mutex_unlock(&clk->mutex); + up_read(&clk->rwsem); return NULL; } static void put_posix_clock(struct posix_clock *clk) { - mutex_unlock(&clk->mutex); + up_read(&clk->rwsem); } static ssize_t posix_clock_read(struct file *fp, char __user *buf, @@ -156,7 +155,7 @@ static int posix_clock_open(struct inode *inode, struct file *fp) struct posix_clock *clk = container_of(inode->i_cdev, struct posix_clock, cdev); - mutex_lock(&clk->mutex); + down_read(&clk->rwsem); if (clk->zombie) { err = -ENODEV; @@ -172,7 +171,7 @@ static int posix_clock_open(struct inode *inode, struct file *fp) fp->private_data = clk; } out: - mutex_unlock(&clk->mutex); + up_read(&clk->rwsem); return err; } @@ -211,25 +210,20 @@ int posix_clock_register(struct posix_clock *clk, dev_t devid) int err; kref_init(&clk->kref); - mutex_init(&clk->mutex); + init_rwsem(&clk->rwsem); cdev_init(&clk->cdev, &posix_clock_file_operations); clk->cdev.owner = clk->ops.owner; err = cdev_add(&clk->cdev, devid, 1); - if (err) - goto no_cdev; return err; -no_cdev: - mutex_destroy(&clk->mutex); - return err; } EXPORT_SYMBOL_GPL(posix_clock_register); static void delete_clock(struct kref *kref) { struct posix_clock *clk = container_of(kref, struct posix_clock, kref); - mutex_destroy(&clk->mutex); + if (clk->release) clk->release(clk); } @@ -238,9 +232,9 @@ void posix_clock_unregister(struct posix_clock *clk) { cdev_del(&clk->cdev); - mutex_lock(&clk->mutex); + down_write(&clk->rwsem); clk->zombie = true; - mutex_unlock(&clk->mutex); + up_write(&clk->rwsem); kref_put(&clk->kref, delete_clock); } From 2dd93c4f47d506c586b827d75646a4257aafa43e Mon Sep 17 00:00:00 2001 From: Axel Lin Date: Sun, 17 Apr 2011 10:02:58 +0800 Subject: [PATCH 2/2] RTC: rtc-omap: Fix a leak of the IRQ during init failure In omap_rtc_probe error path, free_irq() was using NULL rather than the driver data as the data pointer so free_irq() wouldn't have matched. Signed-off-by: Axel Lin Cc: "George G. Davis" Cc: Alessandro Zummo Cc: rtc-linux@googlegroups.com Link: http://lkml.kernel.org/r/%3C1303005778.2889.2.camel%40phoenix%3E Signed-off-by: Thomas Gleixner --- drivers/rtc/rtc-omap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/rtc/rtc-omap.c b/drivers/rtc/rtc-omap.c index de0dd7b1f14..bcae8dd4149 100644 --- a/drivers/rtc/rtc-omap.c +++ b/drivers/rtc/rtc-omap.c @@ -394,7 +394,7 @@ static int __init omap_rtc_probe(struct platform_device *pdev) return 0; fail2: - free_irq(omap_rtc_timer, NULL); + free_irq(omap_rtc_timer, rtc); fail1: rtc_device_unregister(rtc); fail0: