On 7/10/21 10:43 AM, David Lechner wrote:
On 7/10/21 5:25 AM, William Breathitt Gray wrote:
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]
Jarkko
I'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)?
