linux-kernel - [PATCH RFC 1/3] timekeeping: Remove support for old vsyscalls

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Message-Id: <20170517161317.19557-2-mlichvar@redhat.com>
Date:   Wed, 17 May 2017 18:13:15 +0200
From:   Miroslav Lichvar <mlichvar@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     John Stultz <john.stultz@...aro.org>,
        Prarit Bhargava <prarit@...hat.com>,
        Richard Cochran <richardcochran@...il.com>
Subject: [PATCH RFC 1/3] timekeeping: Remove support for old vsyscalls

As the last users of CONFIG_GENERIC_TIME_VSYSCALL_OLD have been updated,
the support can be removed from the timekeeping code.

Cc: John Stultz <john.stultz@...aro.org>
Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Richard Cochran <richardcochran@...il.com>
Signed-off-by: Miroslav Lichvar <mlichvar@...hat.com>
---
 include/linux/timekeeper_internal.h |  7 ------
 kernel/time/Kconfig                 |  4 ----
 kernel/time/timekeeping.c           | 44 -------------------------------------
 3 files changed, 55 deletions(-)

diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h
index 110f453..b7ae5b0 100644
--- a/include/linux/timekeeper_internal.h
+++ b/include/linux/timekeeper_internal.h
@@ -132,13 +132,6 @@ struct timekeeper {
 extern void update_vsyscall(struct timekeeper *tk);
 extern void update_vsyscall_tz(void);
 
-#elif defined(CONFIG_GENERIC_TIME_VSYSCALL_OLD)
-
-extern void update_vsyscall_old(struct timespec *ts, struct timespec *wtm,
-				struct clocksource *c, u32 mult,
-				u64 cycle_last);
-extern void update_vsyscall_tz(void);
-
 #else
 
 static inline void update_vsyscall(struct timekeeper *tk)
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 4008d9f..55d61a3 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -21,10 +21,6 @@ config CLOCKSOURCE_VALIDATE_LAST_CYCLE
 config GENERIC_TIME_VSYSCALL
 	bool
 
-# Timekeeping vsyscall support
-config GENERIC_TIME_VSYSCALL_OLD
-	bool
-
 # Old style timekeeping
 config ARCH_USES_GETTIMEOFFSET
 	bool
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 8fd77c6..ff542dd 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -487,44 +487,6 @@ static void halt_fast_timekeeper(struct timekeeper *tk)
 	update_fast_timekeeper(&tkr_dummy, &tk_fast_raw);
 }
 
-#ifdef CONFIG_GENERIC_TIME_VSYSCALL_OLD
-
-static inline void update_vsyscall(struct timekeeper *tk)
-{
-	struct timespec xt, wm;
-
-	xt = timespec64_to_timespec(tk_xtime(tk));
-	wm = timespec64_to_timespec(tk->wall_to_monotonic);
-	update_vsyscall_old(&xt, &wm, tk->tkr_mono.clock, tk->tkr_mono.mult,
-			    tk->tkr_mono.cycle_last);
-}
-
-static inline void old_vsyscall_fixup(struct timekeeper *tk)
-{
-	s64 remainder;
-
-	/*
-	* Store only full nanoseconds into xtime_nsec after rounding
-	* it up and add the remainder to the error difference.
-	* XXX - This is necessary to avoid small 1ns inconsistnecies caused
-	* by truncating the remainder in vsyscalls. However, it causes
-	* additional work to be done in timekeeping_adjust(). Once
-	* the vsyscall implementations are converted to use xtime_nsec
-	* (shifted nanoseconds), and CONFIG_GENERIC_TIME_VSYSCALL_OLD
-	* users are removed, this can be killed.
-	*/
-	remainder = tk->tkr_mono.xtime_nsec & ((1ULL << tk->tkr_mono.shift) - 1);
-	if (remainder != 0) {
-		tk->tkr_mono.xtime_nsec -= remainder;
-		tk->tkr_mono.xtime_nsec += 1ULL << tk->tkr_mono.shift;
-		tk->ntp_error += remainder << tk->ntp_error_shift;
-		tk->ntp_error -= (1ULL << tk->tkr_mono.shift) << tk->ntp_error_shift;
-	}
-}
-#else
-#define old_vsyscall_fixup(tk)
-#endif
-
 static RAW_NOTIFIER_HEAD(pvclock_gtod_chain);
 
 static void update_pvclock_gtod(struct timekeeper *tk, bool was_set)
@@ -2065,12 +2027,6 @@ void update_wall_time(void)
 	timekeeping_adjust(tk, offset);
 
 	/*
-	 * XXX This can be killed once everyone converts
-	 * to the new update_vsyscall.
-	 */
-	old_vsyscall_fixup(tk);
-
-	/*
 	 * Finally, make sure that after the rounding
 	 * xtime_nsec isn't larger than NSEC_PER_SEC
 	 */
-- 
2.9.3