- Add a new simple facility for marking the current thread as being in a

  state where sleeping on a sleep queue is not allowed.  The facility
  doesn't support recursion but uses a simple private per-thread flag
  (TDP_NOSLEEPING).  The sleepq_add() function will panic if the flag is
  set and INVARIANTS is enabled.
- Use this new facility to replace the g_xup and g_xdown mutexes that were
  (ab)used to achieve similar behavior.
- Disallow sleeping in interrupt threads when invoking interrupt handlers.

MFC after:	1 week
Reviewed by:	phk

1 files changed, 4 insertions, 0 deletions

diff --git a/sys/kern/subr_sleepqueue.c b/sys/kern/subr_sleepqueue.c
index 44a2596..3def263 100644
--- a/sys/kern/subr_sleepqueue.c
+++ b/sys/kern/subr_sleepqueue.c
@@ -269,6 +269,10 @@ sleepq_add(void *wchan, struct mtx *lock, const char *wmesg, int flags)
 	MPASS(td->td_sleepqueue != NULL);
 	MPASS(wchan != NULL);
 
+	/* If this thread is not allowed to sleep, die a horrible death. */
+	KASSERT(!(td->td_pflags & TDP_NOSLEEPING),
+	    ("trying to sleep while sleeping is prohibited"));
+
 	/* Look up the sleep queue associated with the wait channel 'wchan'. */
 	sq = sleepq_lookup(wchan);