On Thu, 4 Apr 2019 00:21:34 +0200
Samuel Thibault <samuel.thibault@xxxxxxxxxxxx> wrote:
> But can't just just get the kref in set_selection before using
> cmpxchg? and if that fails, put it back. If it succeeded, the work
> schedule will happen, and either it will manage to take the tty and
> put its kref, or be canceled, and the kref will be put as well.
Thinking about it, we can also make use of return value of
cancel_work_sync(). It returns true if work was pending. So, if no work
was pending then we don't need to do anything as the kref would be
balanced and the tty would be set to NULL by the time
cancel_work_sync() returns. This would make speakup_cancel_selection()
simpler:
void speakup_cancel_selection(void)
{
struct tty_struct *tty;
bool was_pending;
was_pending = cancel_work_sync(&speakup_sel_work.work);
if (!was_pending)
return;
tty_kref_put(speakup_sel_work.tty);
speakup_sel_work.tty = NULL;
}
We will still need to get kref before cmpxchg() as you suggested above.
Let me know what you think.
Thanks,
Okash
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