[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20240325064023.2997-17-adrian.hunter@intel.com>
Date: Mon, 25 Mar 2024 08:40:20 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Michael Ellerman <mpe@...erman.id.au>,
Nicholas Piggin <npiggin@...il.com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
"Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
Heiko Carstens <hca@...ux.ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
Alexander Gordeev <agordeev@...ux.ibm.com>,
Christian Borntraeger <borntraeger@...ux.ibm.com>,
Sven Schnelle <svens@...ux.ibm.com>,
Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>,
Andy Lutomirski <luto@...nel.org>,
Vincenzo Frascino <vincenzo.frascino@....com>,
John Stultz <jstultz@...gle.com>,
Stephen Boyd <sboyd@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Randy Dunlap <rdunlap@...radead.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Arnd Bergmann <arnd@...db.de>,
Anna-Maria Behnsen <anna-maria@...utronix.de>,
linuxppc-dev@...ts.ozlabs.org,
linux-kernel@...r.kernel.org,
linux-s390@...r.kernel.org
Subject: [PATCH V2 16/19] timekeeping: Prepare timekeeping_cycles_to_ns() for overflow safety
Open code clocksource_delta() in timekeeping_cycles_to_ns() so that
overflow safety can be added efficiently.
Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Adrian Hunter <adrian.hunter@...el.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
Powered by blists - more mailing lists