From: Adrian Hunter <adrian.hunter@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
John Stultz <jstultz@google.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
linux-s390@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
x86@kernel.org, "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>,
Ingo Molnar <mingo@redhat.com>,
"Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Heiko Carstens <hca@linux.ibm.com>,
Nicholas Piggin <npiggin@gmail.com>,
Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
Anna-Maria Behnsen <anna-maria@linutronix.de>,
Stephen Boyd <sboyd@kernel.org>,
Randy Dunlap <rdunlap@infradead.org>,
linux-kernel@vger.kernel.org, Sven Schnelle <svens@linux.ibm.com>,
linuxppc-dev@lists.ozlabs.org
Subject: [PATCH 16/19] timekeeping: Prepare timekeeping_cycles_to_ns() for overflow safety
Date: Fri, 8 Mar 2024 15:15:09 +0200 [thread overview]
Message-ID: <20240308131512.44324-17-adrian.hunter@intel.com> (raw)
In-Reply-To: <20240308131512.44324-1-adrian.hunter@intel.com>
Open code clocksource_delta() in timekeeping_cycles_to_ns() so that
overflow safety can be added efficiently.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
kernel/time/timekeeping.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 749387f22f0f..d17484082e2c 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -367,7 +367,17 @@ static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)
static inline u64 timekeeping_cycles_to_ns(const struct tk_read_base *tkr, u64 cycles)
{
/* Calculate the delta since the last update_wall_time() */
- u64 delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
+ u64 mask = tkr->mask, delta = (cycles - tkr->cycle_last) & mask;
+
+ if (IS_ENABLED(CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE)) {
+ /*
+ * Handle clocksource inconsistency between CPUs to prevent
+ * time from going backwards by checking for the MSB of the
+ * mask being set in the delta.
+ */
+ if (unlikely(delta & ~(mask >> 1)))
+ return tkr->xtime_nsec >> tkr->shift;
+ }
return ((delta * tkr->mult) + tkr->xtime_nsec) >> tkr->shift;
}
--
2.34.1
next prev parent reply other threads:[~2024-03-08 13:26 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-08 13:14 [PATCH 00/19] timekeeping: Handle potential multiplication overflow Adrian Hunter
2024-03-08 13:14 ` [PATCH 01/19] vdso: Consolidate vdso_calc_delta() Adrian Hunter
2024-03-09 2:09 ` John Stultz
2024-03-09 7:48 ` Christophe Leroy
2024-03-08 13:14 ` [PATCH 02/19] vdso: Consolidate nanoseconds calculation Adrian Hunter
2024-03-08 13:14 ` [PATCH 03/19] vdso: Add CONFIG_GENERIC_VDSO_OVERFLOW_PROTECT Adrian Hunter
2024-03-08 13:14 ` [PATCH 04/19] math64: Tidy mul_u64_u32_shr() Adrian Hunter
2024-03-08 13:14 ` [PATCH 05/19] vdso: math64: Provide mul_u64_u32_add_u64_shr() Adrian Hunter
2024-03-08 13:14 ` [PATCH 06/19] vdso: Add vdso_data::max_cycles Adrian Hunter
2024-03-08 13:15 ` [PATCH 07/19] vdso: Make delta calculation overflow safe Adrian Hunter
2024-03-08 13:15 ` [PATCH 08/19] x86/vdso: " Adrian Hunter
2024-03-08 13:15 ` [PATCH 09/19] timekeeping: Move timekeeping helper functions Adrian Hunter
2024-03-08 13:15 ` [PATCH 10/19] timekeeping: Rename fast_tk_get_delta_ns() to __timekeeping_get_ns() Adrian Hunter
2024-03-08 13:15 ` [PATCH 11/19] timekeeping: Tidy timekeeping_cycles_to_ns() slightly Adrian Hunter
2024-03-08 13:15 ` [PATCH 12/19] timekeeping: Reuse timekeeping_cycles_to_ns() Adrian Hunter
2024-03-08 13:15 ` [PATCH 13/19] timekeeping: Refactor timekeeping helpers Adrian Hunter
2024-03-08 13:15 ` [PATCH 14/19] timekeeping: Consolidate " Adrian Hunter
2024-03-08 13:15 ` [PATCH 15/19] timekeeping: Fold in timekeeping_delta_to_ns() Adrian Hunter
2024-03-08 13:15 ` Adrian Hunter [this message]
2024-03-08 13:15 ` [PATCH 17/19] timekeeping: Make delta calculation overflow safe Adrian Hunter
2024-03-08 13:15 ` [PATCH 18/19] timekeeping: Let timekeeping_cycles_to_ns() handle both under and overflow Adrian Hunter
2024-03-08 13:15 ` [PATCH 19/19] clocksource: Make watchdog and suspend-timing multiplication overflow safe Adrian Hunter
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