From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx127.postini.com [74.125.245.127]) by kanga.kvack.org (Postfix) with SMTP id C23436B004D for ; Sun, 8 Apr 2012 19:38:11 -0400 (EDT) Received: by bkwq16 with SMTP id q16so4000567bkw.14 for ; Sun, 08 Apr 2012 16:38:10 -0700 (PDT) Date: Mon, 9 Apr 2012 03:38:02 +0400 From: Anton Vorontsov Subject: [PATCH 1/3] vmevent: Should not grab mutex in the atomic context Message-ID: <20120408233802.GA4839@panacea> References: <20120408233550.GA3791@panacea> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20120408233550.GA3791@panacea> Sender: owner-linux-mm@kvack.org List-ID: To: Pekka Enberg Cc: Leonid Moiseichuk , John Stultz , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linaro-kernel@lists.linaro.org vmevent grabs a mutex in the atomic context, and so this pops up: BUG: sleeping function called from invalid context at kernel/mutex.c:271 in_atomic(): 1, irqs_disabled(): 0, pid: 0, name: swapper/0 1 lock held by swapper/0/0: #0: (&watch->timer){+.-...}, at: [] call_timer_fn+0x0/0xf0 Pid: 0, comm: swapper/0 Not tainted 3.2.0+ #6 Call Trace: [] __might_sleep+0x12a/0x1e0 [] ? vmevent_match+0xe0/0xe0 [] mutex_lock_nested+0x3c/0x340 [] ? lock_acquire+0xa3/0xc0 [] ? internal_add_timer+0x110/0x110 [] ? vmevent_match+0xe0/0xe0 [] vmevent_timer_fn+0x91/0xf0 [] ? vmevent_match+0xe0/0xe0 [] call_timer_fn+0x75/0xf0 [] ? internal_add_timer+0x110/0x110 [] ? trace_hardirqs_on_caller+0x7d/0x120 [] run_timer_softirq+0x10f/0x1e0 [] ? vmevent_match+0xe0/0xe0 [] __do_softirq+0xb0/0x160 [] ? tick_program_event+0x1f/0x30 [] call_softirq+0x1c/0x26 [] do_softirq+0x85/0xc0 This patch fixes the issue by removing the mutex and making the logic lock-free. Signed-off-by: Anton Vorontsov --- mm/vmevent.c | 35 ++++++++++++----------------------- 1 files changed, 12 insertions(+), 23 deletions(-) diff --git a/mm/vmevent.c b/mm/vmevent.c index 1847b56..a56174f 100644 --- a/mm/vmevent.c +++ b/mm/vmevent.c @@ -1,4 +1,5 @@ #include +#include #include #include #include @@ -23,7 +24,7 @@ struct vmevent_watch { struct vmevent_config config; struct mutex mutex; - bool pending; + atomic_t pending; /* * Attributes that are exported as part of delivered VM events. @@ -103,20 +104,18 @@ static void vmevent_sample(struct vmevent_watch *watch) { int i; + if (atomic_read(&watch->pending)) + return; if (!vmevent_match(watch)) return; - mutex_lock(&watch->mutex); - - watch->pending = true; - for (i = 0; i < watch->nr_attrs; i++) { struct vmevent_attr *attr = &watch->sample_attrs[i]; attr->value = vmevent_sample_attr(watch, attr); } - mutex_unlock(&watch->mutex); + atomic_set(&watch->pending, 1); } static void vmevent_timer_fn(unsigned long data) @@ -125,7 +124,7 @@ static void vmevent_timer_fn(unsigned long data) vmevent_sample(watch); - if (watch->pending) + if (atomic_read(&watch->pending)) wake_up(&watch->waitq); mod_timer(&watch->timer, jiffies + nsecs_to_jiffies64(watch->config.sample_period_ns)); @@ -148,13 +147,9 @@ static unsigned int vmevent_poll(struct file *file, poll_table *wait) poll_wait(file, &watch->waitq, wait); - mutex_lock(&watch->mutex); - - if (watch->pending) + if (atomic_read(&watch->pending)) events |= POLLIN; - mutex_unlock(&watch->mutex); - return events; } @@ -171,15 +166,13 @@ static ssize_t vmevent_read(struct file *file, char __user *buf, size_t count, l if (count < size) return -EINVAL; - mutex_lock(&watch->mutex); - - if (!watch->pending) - goto out_unlock; + if (!atomic_read(&watch->pending)) + goto out; event = kmalloc(size, GFP_KERNEL); if (!event) { ret = -ENOMEM; - goto out_unlock; + goto out; } for (i = 0; i < watch->nr_attrs; i++) { @@ -195,14 +188,10 @@ static ssize_t vmevent_read(struct file *file, char __user *buf, size_t count, l ret = count; - watch->pending = false; - + atomic_set(&watch->pending, 0); out_free: kfree(event); - -out_unlock: - mutex_unlock(&watch->mutex); - +out: return ret; } -- 1.7.7.6 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org