Re: [PATCH v12 15/17] counter: Implement events_queue_size sysfs attribute
From: David Lechner <david@lechnology.com>
Date: 2021-07-10 16:08:32
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On 7/10/21 10:43 AM, David Lechner wrote:
On 7/10/21 5:25 AM, William Breathitt Gray wrote:quoted
quoted
and after that [ 16.564403] ================================================ [ 16.570725] WARNING: lock held when returning to user space! [ 16.577044] 5.13.0-next-20210706+ #4 Not tainted [ 16.582198] ------------------------------------------------ [ 16.588507] cat/331 is leaving the kernel with locks still held! [ 16.595214] 1 lock held by cat/331: [ 16.599103] #0: ffff888102bb3630 (&counter->chrdev_lock){+.+.}-{3:3}, at: counter_chrdev_open+0x21/0x60 [counter] JarkkoI'm not sure how to resolve this warning. The purpose of this lock is to limit chrdev to a single open at a time. To accomplish this I grab this lock in counter_chrdev_open() and hold it until counter_chrdev_release() is called. Is there a better way to accomplish this?How about using an atomic flag, e.g test_and_set_bit()?
Another option could be to rethink it at a higher level and avoid the need for a lock (and sysfs attribute) altogether. For example, would it work to (re)allocate the kfifo buffer in the COUNTER_ENABLE_EVENTS_IOCTL callback and add a parameter to that ioctl to specify the buffer size (with units of events rather than bytes)? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel