Major callout subsystem cleanup and rewrite:

- Close a migration race where callout_reset() failed to set the
  CALLOUT_ACTIVE flag.
- Callout callback functions are now allowed to be protected by
  spinlocks.
- Switching the callout CPU number cannot always be done on a
  per-callout basis. See the updated timeout(9) manual page for more
  information.
- The timeout(9) manual page has been updated to reflect how all the
  functions inside the callout API are working. The manual page has
  been made function oriented to make it easier to deduce how each of
  the functions making up the callout API are working without having
  to first read the whole manual page. Group all functions into a
  handful of sections which should give a quick top-level overview
  when the different functions should be used.
- The CALLOUT_SHAREDLOCK flag and its functionality has been removed
  to reduce the complexity in the callout code and to avoid problems
  about atomically stopping callouts via callout_stop(). If someone
  needs it, it can be re-added. From my quick grep there are no
  CALLOUT_SHAREDLOCK clients in the kernel.
- A new callout API function named "callout_drain_async()" has been
  added. See the updated timeout(9) manual page for a complete
  description.
- Update the callout clients in the "kern/" folder to use the callout
  API properly, like cv_timedwait(). Previously there was some custom
  sleepqueue code in the callout subsystem, which has been removed,
  because we now allow callouts to be protected by spinlocks. This
  allows us to tear down the callout like done with regular mutexes,
  and a "td_slpmutex" has been added to "struct thread" to atomically
  teardown the "td_slpcallout". Further the "TDF_TIMOFAIL" and
  "SWT_SLEEPQTIMO" states can now be completely removed. Currently
  they are marked as available and will be cleaned up in a follow up
  commit.
- Bump the __FreeBSD_version to indicate kernel modules need
  recompilation.
- There has been several reports that this patch "seems to squash a
  serious bug leading to a callout timeout and panic".

Kernel build testing:	all architectures were built
MFC after:		2 weeks
Differential Revision:	https://reviews.freebsd.org/D1438
Sponsored by:		Mellanox Technologies
Reviewed by:		jhb, adrian, sbruno and emaste

1 files changed, 8 insertions, 6 deletions

diff --git a/sys/sys/callout.h b/sys/sys/callout.h
index 1096cb2..235da99 100644
--- a/sys/sys/callout.h
+++ b/sys/sys/callout.h
@@ -45,10 +45,12 @@
 #define	CALLOUT_PENDING		0x0004 /* callout is waiting for timeout */
 #define	CALLOUT_MPSAFE		0x0008 /* callout handler is mp safe */
 #define	CALLOUT_RETURNUNLOCKED	0x0010 /* handler returns with mtx unlocked */
-#define	CALLOUT_SHAREDLOCK	0x0020 /* callout lock held in shared mode */
-#define	CALLOUT_DFRMIGRATION	0x0040 /* callout in deferred migration mode */
+#define	CALLOUT_UNUSED_5	0x0020 /* --available-- */
+#define	CALLOUT_DEFRESTART	0x0040 /* callout restart is deferred */
 #define	CALLOUT_PROCESSED	0x0080 /* callout in wheel or processing list? */
 #define	CALLOUT_DIRECT 		0x0100 /* allow exec from hw int context */
+#define	CALLOUT_SET_LC(x)	(((x) & 7) << 16) /* set lock class */
+#define	CALLOUT_GET_LC(x)	(((x) >> 16) & 7) /* get lock class */
 
 #define	C_DIRECT_EXEC		0x0001 /* direct execution of callout */
 #define	C_PRELBITS		7
@@ -65,7 +67,8 @@ struct callout_handle {
 #ifdef _KERNEL
 #define	callout_active(c)	((c)->c_flags & CALLOUT_ACTIVE)
 #define	callout_deactivate(c)	((c)->c_flags &= ~CALLOUT_ACTIVE)
-#define	callout_drain(c)	_callout_stop_safe(c, 1)
+int	callout_drain(struct callout *);
+int	callout_drain_async(struct callout *, callout_func_t *, void *);
 void	callout_init(struct callout *, int);
 void	_callout_init_lock(struct callout *, struct lock_object *, int);
 #define	callout_init_mtx(c, mtx, flags)					\
@@ -79,7 +82,7 @@ void	_callout_init_lock(struct callout *, struct lock_object *, int);
 	   NULL, (flags))
 #define	callout_pending(c)	((c)->c_flags & CALLOUT_PENDING)
 int	callout_reset_sbt_on(struct callout *, sbintime_t, sbintime_t,
-	    void (*)(void *), void *, int, int);
+	    callout_func_t *, void *, int, int);
 #define	callout_reset_sbt(c, sbt, pr, fn, arg, flags)			\
     callout_reset_sbt_on((c), (sbt), (pr), (fn), (arg), (c)->c_cpu, (flags))
 #define	callout_reset_sbt_curcpu(c, sbt, pr, fn, arg, flags)		\
@@ -103,8 +106,7 @@ int	callout_schedule(struct callout *, int);
 int	callout_schedule_on(struct callout *, int, int);
 #define	callout_schedule_curcpu(c, on_tick)				\
     callout_schedule_on((c), (on_tick), PCPU_GET(cpuid))
-#define	callout_stop(c)		_callout_stop_safe(c, 0)
-int	_callout_stop_safe(struct callout *, int);
+int	callout_stop(struct callout *);
 void	callout_process(sbintime_t now);
 
 #endif