UserEvent can be fired from scheduler_reschedule() i.e. while holding current
thread scheduler_lock. If the current thread goes sleep and during reschedule
one of its timers sends a signel to it, then scheduler_enqueue_in_run_queue()
attempts to acquire again its scheduler_lock resulting in a deadlock.
There was also a minor issue with both scheduler_reschedule() and
scheduler_enqueue_in_run_queue() acquiring current CPU scheduler mode lock.
* Reorganized the kernel locking related to threads and teams.
* We now discriminate correctly between process and thread signals. Signal
handlers have been moved to teams. Fixes #5679.
* Implemented real-time signal support, including signal queuing, SA_SIGINFO
support, sigqueue(), sigwaitinfo(), sigtimedwait(), waitid(), and the addition
of the real-time signal range. Closes #1935 and #2695.
* Gave SIGBUS a separate signal number. Fixes #6704.
* Implemented <time.h> clock and timer support, and fixed/completed alarm() and
[set]itimer(). Closes #5682.
* Implemented support for thread cancellation. Closes #5686.
* Moved send_signal() from <signal.h> to <OS.h>. Fixes #7554.
* Lots over smaller more or less related changes.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42116 a95241bf-73f2-0310-859d-f6bbb57e9c96
