Emulate illumos interface cv_timedwait_hires()

Needed for Illumos #3582. This interface is supposed to support
a variable-resolution timeout with nanosecond granularity.  This
implementation rounds up to microsecond resolution, as nanosecond-
precision timing is rarely needed for real-world performance
tuning and may incur unnecessary busy-waiting.  usleep_range() is
used if available, otherwise udelay() or msleep() are used
depending on the length of the delay interval.

Add flags from sys/callo.h as these are used to control the behavior of
cv_timedwait_hires().  Specifically,

CALLOUT_FLAG_ABSOLUTE
    Normally, the expiration passed to the timeout API functions is
    an expiration interval. If this flag is specified, then it is
    interpreted as the expiration time itself.

CALLOUT_FLAG_ROUNDUP
    Roundup the expiration time to the next resolution boundary. If this
    flag is not specified, the expiration time is rounded down.

References:
    https://www.illumos.org/issues/3582
    illumos/illumos-gate@0689f76

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #304

config/spl-build.m4

@@ -93,6 +93,7 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [
 	SPL_AC_RWSEM_SPINLOCK_IS_RAW
 	SPL_AC_SCHED_RT_HEADER
 	SPL_AC_2ARGS_VFS_GETATTR
+	SPL_AC_USLEEP_RANGE
 ])
 
 AC_DEFUN([SPL_AC_MODULE_SYMVERS], [
@@ -2400,3 +2401,25 @@ AC_DEFUN([SPL_AC_2ARGS_VFS_GETATTR], [
 		])
 	])
 ])
+
+dnl #
+dnl # 2.6.36 API compatibility.
+dnl # Added usleep_range timer.
+dnl # usleep_range is a finer precision implementation of msleep
+dnl # designed to be a drop-in replacement for udelay where a precise
+dnl # sleep / busy-wait is unnecessary.
+dnl #
+AC_DEFUN([SPL_AC_USLEEP_RANGE], [
+	AC_MSG_CHECKING([whether usleep_range() is available])
+	SPL_LINUX_TRY_COMPILE([
+		#include <linux/delay.h>
+	],[
+		usleep_range(0, 0);
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_USLEEP_RANGE, 1,
+		          [usleep_range is available])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])

include/linux/Makefile.am

@@ -3,6 +3,7 @@ COMMON_H =
 KERNEL_H = \
 	$(top_srcdir)/include/linux/bitops_compat.h \
 	$(top_srcdir)/include/linux/compiler_compat.h \
+	$(top_srcdir)/include/linux/delay_compat.h \
 	$(top_srcdir)/include/linux/file_compat.h \
 	$(top_srcdir)/include/linux/kallsyms_compat.h \
 	$(top_srcdir)/include/linux/list_compat.h \

include/linux/delay_compat.h

@@ -0,0 +1,47 @@
+/*****************************************************************************\
+ *  Copyright (C) 2007-2013 Lawrence Livermore National Security, LLC.
+ *  Copyright (C) 2007 The Regents of the University of California.
+ *  Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
+ *  Written by Brian Behlendorf <behlendorf1@llnl.gov>.
+ *  UCRL-CODE-235197
+ *
+ *  This file is part of the SPL, Solaris Porting Layer.
+ *  For details, see <http://zfsonlinux.org/>.
+ *
+ *  The SPL is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License as published by the
+ *  Free Software Foundation; either version 2 of the License, or (at your
+ *  option) any later version.
+ *
+ *  The SPL is distributed in the hope that it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ *  for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
+\*****************************************************************************/
+
+#ifndef _SPL_DELAY_COMPAT_H
+#define _SPL_DELAY_COMPAT_H
+
+#include <linux/delay.h>
+#include <linux/time.h>
+
+/* usleep_range() introduced in 2.6.36 */
+#ifndef HAVE_USLEEP_RANGE
+
+static inline void
+usleep_range(unsigned long min, unsigned long max)
+{
+	unsigned int min_ms = min / USEC_PER_MSEC;
+
+	if (min >= MAX_UDELAY_MS)
+		msleep(min_ms);
+	else
+		udelay(min);
+}
+
+#endif /* HAVE_USLEEP_RANGE */
+
+#endif /* _SPL_DELAY_COMPAT_H */

include/sys/Makefile.am

@@ -13,6 +13,7 @@ KERNEL_H = \
 	$(top_srcdir)/include/sys/buf.h \
 	$(top_srcdir)/include/sys/byteorder.h \
 	$(top_srcdir)/include/sys/callb.h \
+	$(top_srcdir)/include/sys/callo.h \
 	$(top_srcdir)/include/sys/cmn_err.h \
 	$(top_srcdir)/include/sys/compress.h \
 	$(top_srcdir)/include/sys/condvar.h \

include/sys/callo.h

@@ -0,0 +1,52 @@
+/*****************************************************************************\
+ *  Copyright (C) 2007-2013 Lawrence Livermore National Security, LLC.
+ *  Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
+ *  Written by Brian Behlendorf <behlendorf1@llnl.gov>.
+ *  UCRL-CODE-235197
+ *
+ *  This file is part of the SPL, Solaris Porting Layer.
+ *  For details, see <http://zfsonlinux.org/>.
+ *
+ *  The SPL is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License as published by the
+ *  Free Software Foundation; either version 2 of the License, or (at your
+ *  option) any later version.
+ *
+ *  The SPL is distributed in the hope that it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ *  for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
+\*****************************************************************************/
+
+#ifndef _SPL_CALLO_H
+#define _SPL_CALLO_H
+
+/*
+ * Callout flags:
+ *
+ * CALLOUT_FLAG_ROUNDUP
+ *      Roundup the expiration time to the next resolution boundary.
+ *      If this flag is not specified, the expiration time is rounded down.
+ * CALLOUT_FLAG_ABSOLUTE
+ *      Normally, the expiration passed to the timeout API functions is an
+ *      expiration interval. If this flag is specified, then it is
+ *      interpreted as the expiration time itself.
+ * CALLOUT_FLAG_HRESTIME
+ *      Normally, callouts are not affected by changes to system time
+ *      (hrestime). This flag is used to create a callout that is affected
+ *      by system time. If system time changes, these timers must be
+ *      handled in a special way (see callout.c). These are used by condition
+ *      variables and LWP timers that need this behavior.
+ * CALLOUT_FLAG_32BIT
+ *      Legacy interfaces timeout() and realtime_timeout() pass this flag
+ *      to timeout_generic() to indicate that a 32-bit ID should be allocated.
+ */
+#define CALLOUT_FLAG_ROUNDUP            0x1
+#define CALLOUT_FLAG_ABSOLUTE           0x2
+#define CALLOUT_FLAG_HRESTIME           0x4
+#define CALLOUT_FLAG_32BIT              0x8
+
+#endif  /* _SPL_CALLB_H */

include/sys/condvar.h

@@ -27,8 +27,10 @@
 
 #include <linux/module.h>
 #include <linux/wait.h>
+#include <linux/delay_compat.h>
 #include <sys/kmem.h>
 #include <sys/mutex.h>
+#include <sys/callo.h>
 
 /*
  * The kcondvar_t struct is protected by mutex taken externally before
@@ -56,6 +58,8 @@ extern void __cv_wait_interruptible(kcondvar_t *cvp, kmutex_t *mp);
 extern clock_t __cv_timedwait(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time);
 extern clock_t __cv_timedwait_interruptible(kcondvar_t *cvp, kmutex_t *mp,
 	clock_t exp_time);
+extern	clock_t	cv_timedwait_hires(kcondvar_t *cvp, kmutex_t *mp,
+	hrtime_t tim, hrtime_t res, int flag);
 extern void __cv_signal(kcondvar_t *cvp);
 extern void __cv_broadcast(kcondvar_t *cvp);
 

include/sys/time.h

@@ -47,6 +47,9 @@
 #define MICROSEC			1000000
 #define NANOSEC				1000000000
 
+#define	MSEC2NSEC(m)	((hrtime_t)(m) * (NANOSEC / MILLISEC))
+#define	NSEC2MSEC(n)	((n) / (NANOSEC / MILLISEC))
+
 /* Already defined in include/linux/time.h */
 #undef CLOCK_THREAD_CPUTIME_ID
 #undef CLOCK_REALTIME

module/spl/spl-condvar.c

@@ -226,6 +226,87 @@ __cv_timedwait_interruptible(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time)
 }
 EXPORT_SYMBOL(__cv_timedwait_interruptible);
 
+/*
+ *'expire_time' argument is an absolute clock time in nanoseconds.
+ * Return value is time left (expire_time - now) or -1 if timeout occurred.
+ */
+static clock_t
+__cv_timedwait_hires(kcondvar_t *cvp, kmutex_t *mp,
+		     hrtime_t expire_time, int state)
+{
+	DEFINE_WAIT(wait);
+	hrtime_t time_left, now;
+	unsigned long time_left_us;
+	SENTRY;
+
+	ASSERT(cvp);
+	ASSERT(mp);
+	ASSERT(cvp->cv_magic == CV_MAGIC);
+	ASSERT(mutex_owned(mp));
+	atomic_inc(&cvp->cv_refs);
+
+	if (cvp->cv_mutex == NULL)
+		cvp->cv_mutex = mp;
+
+	/* Ensure the same mutex is used by all callers */
+	ASSERT(cvp->cv_mutex == mp);
+
+	now = gethrtime();
+	time_left = expire_time - now;
+	if (time_left <= 0) {
+		atomic_dec(&cvp->cv_refs);
+		SRETURN(-1);
+	}
+	time_left_us = time_left / NSEC_PER_USEC;
+
+	prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
+	atomic_inc(&cvp->cv_waiters);
+
+	/* Mutex should be dropped after prepare_to_wait() this
+	 * ensures we're linked in to the waiters list and avoids the
+	 * race where 'cvp->cv_waiters > 0' but the list is empty. */
+	mutex_exit(mp);
+	/* Allow a 100 us range to give kernel an opportunity to coalesce
+	 * interrupts */
+	usleep_range(time_left_us, time_left_us + 100);
+	mutex_enter(mp);
+
+	/* No more waiters a different mutex could be used */
+	if (atomic_dec_and_test(&cvp->cv_waiters)) {
+		cvp->cv_mutex = NULL;
+		wake_up(&cvp->cv_destroy);
+	}
+
+	finish_wait(&cvp->cv_event, &wait);
+	atomic_dec(&cvp->cv_refs);
+
+	time_left = expire_time - gethrtime();
+	SRETURN(time_left > 0 ? time_left : -1);
+}
+
+/*
+ * Compatibility wrapper for the cv_timedwait_hires() Illumos interface.
+ */
+clock_t
+cv_timedwait_hires(kcondvar_t *cvp, kmutex_t *mp, hrtime_t tim,
+		   hrtime_t res, int flag)
+{
+	if (res > 1) {
+		/*
+		 * Align expiration to the specified resolution.
+		 */
+		if (flag & CALLOUT_FLAG_ROUNDUP)
+			tim += res - 1;
+		tim = (tim / res) * res;
+	}
+
+	if (!(flag & CALLOUT_FLAG_ABSOLUTE))
+		tim += gethrtime();
+
+	return __cv_timedwait_hires(cvp, mp, tim, TASK_UNINTERRUPTIBLE);
+}
+EXPORT_SYMBOL(cv_timedwait_hires);
+
 void
 __cv_signal(kcondvar_t *cvp)
 {