From 1deb9d341d475ff84262e927d6c0e36fecb9942e Mon Sep 17 00:00:00 2001 From: Jiri Kosina Date: Mon, 6 May 2013 13:05:50 +0200 Subject: HID: debug: fix RCU preemption issue Commit 2353f2bea ("HID: protect hid_debug_list") introduced mutex locking around debug_list access to prevent SMP races when debugfs nodes are being operated upon by multiple userspace processess. mutex is not a proper synchronization primitive though, as the hid-debug callbacks are being called from atomic contexts. We also have to be careful about disabling IRQs when taking the lock to prevent deadlock against IRQ handlers. Benjamin reports this has also been reported in RH bugzilla as bug #958935. =============================== [ INFO: suspicious RCU usage. ] 3.9.0+ #94 Not tainted ------------------------------- include/linux/rcupdate.h:476 Illegal context switch in RCU read-side critical section! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 0 4 locks held by Xorg/5502: #0: (&evdev->mutex){+.+...}, at: [] evdev_write+0x6d/0x160 #1: (&(&dev->event_lock)->rlock#2){-.-...}, at: [] input_inject_event+0x5b/0x230 #2: (rcu_read_lock){.+.+..}, at: [] input_inject_event+0x42/0x230 #3: (&(&usbhid->lock)->rlock){-.....}, at: [] usb_hidinput_input_event+0x89/0x120 stack backtrace: CPU: 0 PID: 5502 Comm: Xorg Not tainted 3.9.0+ #94 Hardware name: Dell Inc. OptiPlex 390/0M5DCD, BIOS A09 07/24/2012 0000000000000001 ffff8800689c7c38 ffffffff816f249f ffff8800689c7c68 ffffffff810acb1d 0000000000000000 ffffffff81a03ac7 000000000000019d 0000000000000000 ffff8800689c7c90 ffffffff8107cda7 0000000000000000 Call Trace: [] dump_stack+0x19/0x1b [] lockdep_rcu_suspicious+0xfd/0x130 [] __might_sleep+0xc7/0x230 [] mutex_lock_nested+0x40/0x3a0 [] ? vsnprintf+0x354/0x640 [] hid_debug_event+0x34/0x100 [] hid_dump_input+0x67/0xa0 [] hid_set_field+0x50/0x120 [] usb_hidinput_input_event+0x9a/0x120 [] input_handle_event+0x8e/0x530 [] input_inject_event+0x1d0/0x230 [] ? input_inject_event+0x42/0x230 [] evdev_write+0xde/0x160 [] vfs_write+0xc8/0x1f0 [] SyS_write+0x55/0xa0 [] system_call_fastpath+0x16/0x1b BUG: sleeping function called from invalid context at kernel/mutex.c:413 in_atomic(): 1, irqs_disabled(): 1, pid: 5502, name: Xorg INFO: lockdep is turned off. irq event stamp: 1098574 hardirqs last enabled at (1098573): [] _raw_spin_unlock_irqrestore+0x3f/0x70 hardirqs last disabled at (1098574): [] _raw_spin_lock_irqsave+0x25/0xa0 softirqs last enabled at (1098306): [] __do_softirq+0x18f/0x3c0 softirqs last disabled at (1097867): [] irq_exit+0xa5/0xb0 CPU: 0 PID: 5502 Comm: Xorg Not tainted 3.9.0+ #94 Hardware name: Dell Inc. OptiPlex 390/0M5DCD, BIOS A09 07/24/2012 ffffffff81a03ac7 ffff8800689c7c68 ffffffff816f249f ffff8800689c7c90 ffffffff8107ce60 0000000000000000 ffff8800689c7fd8 ffff88006a62c800 ffff8800689c7d10 ffffffff816f7770 ffff8800689c7d00 ffffffff81312ac4 Call Trace: [] dump_stack+0x19/0x1b [] __might_sleep+0x180/0x230 [] mutex_lock_nested+0x40/0x3a0 [] ? vsnprintf+0x354/0x640 [] hid_debug_event+0x34/0x100 [] hid_dump_input+0x67/0xa0 [] hid_set_field+0x50/0x120 [] usb_hidinput_input_event+0x9a/0x120 [] input_handle_event+0x8e/0x530 [] input_inject_event+0x1d0/0x230 [] ? input_inject_event+0x42/0x230 [] evdev_write+0xde/0x160 [] vfs_write+0xc8/0x1f0 [] SyS_write+0x55/0xa0 [] system_call_fastpath+0x16/0x1b Reported-by: majianpeng Reported-by: Benjamin Tissoires Reviewed-by: Dmitry Torokhov Signed-off-by: Jiri Kosina --- drivers/hid/hid-debug.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) (limited to 'drivers/hid/hid-debug.c') diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c index 7e56cb3855e3..8453214ec376 100644 --- a/drivers/hid/hid-debug.c +++ b/drivers/hid/hid-debug.c @@ -579,15 +579,16 @@ void hid_debug_event(struct hid_device *hdev, char *buf) { int i; struct hid_debug_list *list; + unsigned long flags; - mutex_lock(&hdev->debug_list_lock); + spin_lock_irqsave(&hdev->debug_list_lock, flags); list_for_each_entry(list, &hdev->debug_list, node) { for (i = 0; i < strlen(buf); i++) list->hid_debug_buf[(list->tail + i) % HID_DEBUG_BUFSIZE] = buf[i]; list->tail = (list->tail + i) % HID_DEBUG_BUFSIZE; } - mutex_unlock(&hdev->debug_list_lock); + spin_unlock_irqrestore(&hdev->debug_list_lock, flags); wake_up_interruptible(&hdev->debug_wait); } @@ -977,6 +978,7 @@ static int hid_debug_events_open(struct inode *inode, struct file *file) { int err = 0; struct hid_debug_list *list; + unsigned long flags; if (!(list = kzalloc(sizeof(struct hid_debug_list), GFP_KERNEL))) { err = -ENOMEM; @@ -992,9 +994,9 @@ static int hid_debug_events_open(struct inode *inode, struct file *file) file->private_data = list; mutex_init(&list->read_mutex); - mutex_lock(&list->hdev->debug_list_lock); + spin_lock_irqsave(&list->hdev->debug_list_lock, flags); list_add_tail(&list->node, &list->hdev->debug_list); - mutex_unlock(&list->hdev->debug_list_lock); + spin_unlock_irqrestore(&list->hdev->debug_list_lock, flags); out: return err; @@ -1088,10 +1090,11 @@ static unsigned int hid_debug_events_poll(struct file *file, poll_table *wait) static int hid_debug_events_release(struct inode *inode, struct file *file) { struct hid_debug_list *list = file->private_data; + unsigned long flags; - mutex_lock(&list->hdev->debug_list_lock); + spin_lock_irqsave(&list->hdev->debug_list_lock, flags); list_del(&list->node); - mutex_unlock(&list->hdev->debug_list_lock); + spin_unlock_irqrestore(&list->hdev->debug_list_lock, flags); kfree(list->hid_debug_buf); kfree(list); -- cgit v1.2.3