linux-stable.git/kernel/time/timekeeping.c, branch linux-6.10.y

timekeeping: Fix bogus clock_was_set() invocation in do_adjtimex()

2024-08-14T13:34:30+00:00

commit 5916be8a53de6401871bdd953f6c60237b47d6d3 upstream.

The addition of the bases argument to clock_was_set() fixed up all call
sites correctly except for do_adjtimex(). This uses CLOCK_REALTIME
instead of CLOCK_SET_WALL as argument. CLOCK_REALTIME is 0.

As a result the effect of that clock_was_set() notification is incomplete
and might result in timers expiring late because the hrtimer code does
not re-evaluate the affected clock bases.

Use CLOCK_SET_WALL instead of CLOCK_REALTIME to tell the hrtimers code
which clock bases need to be re-evaluated.

Fixes: 17a1b8826b45 ("hrtimer: Add bases argument to clock_was_set()")
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/877ccx7igo.ffs@tglx
Signed-off-by: Greg Kroah-Hartman

timekeeping: Let timekeeping_cycles_to_ns() handle both under and overflow

2024-04-08T13:03:08+00:00

For the case !CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE, forego overflow
protection in the range (mask << 1) < delta <= mask, and interpret it
always as an inconsistency between CPU clock values. That allows
slightly neater code, and it is on a slow path so has no effect on
performance.

Suggested-by: Thomas Gleixner 
Signed-off-by: Adrian Hunter 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20240325064023.2997-19-adrian.hunter@intel.com

timekeeping: Make delta calculation overflow safe

2024-04-08T13:03:08+00:00

Kernel timekeeping is designed to keep the change in cycles (since the last
timer interrupt) below max_cycles, which prevents multiplication overflow
when converting cycles to nanoseconds. However, if timer interrupts stop,
the calculation will eventually overflow.

Add protection against that. In timekeeping_cycles_to_ns() calculation,
check against max_cycles, falling back to a slower higher precision
calculation. In timekeeping_forward_now(), process delta in chunks of at
most max_cycles.

Suggested-by: Thomas Gleixner 
Signed-off-by: Adrian Hunter 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20240325064023.2997-18-adrian.hunter@intel.com

timekeeping: Prepare timekeeping_cycles_to_ns() for overflow safety

2024-04-08T13:03:08+00:00

Open code clocksource_delta() in timekeeping_cycles_to_ns() so that
overflow safety can be added efficiently.

Suggested-by: Thomas Gleixner 
Signed-off-by: Adrian Hunter 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20240325064023.2997-17-adrian.hunter@intel.com

timekeeping: Fold in timekeeping_delta_to_ns()

2024-04-08T13:03:08+00:00

timekeeping_delta_to_ns() is now called only from
timekeeping_cycles_to_ns(), and it is not useful otherwise.

Simplify the code by folding it into timekeeping_cycles_to_ns().

No functional change.

Suggested-by: Thomas Gleixner 
Signed-off-by: Adrian Hunter 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20240325064023.2997-16-adrian.hunter@intel.com

timekeeping: Consolidate timekeeping helpers

2024-04-08T13:03:08+00:00

Consolidate timekeeping helpers, making use of timekeeping_cycles_to_ns()
in preference to directly using timekeeping_delta_to_ns().

No functional change.

Suggested-by: Thomas Gleixner 
Signed-off-by: Adrian Hunter 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20240325064023.2997-15-adrian.hunter@intel.com

timekeeping: Refactor timekeeping helpers

2024-04-08T13:03:08+00:00

Simplify the usage of timekeeping sanity checking, in preparation for
consolidating timekeeping helpers. This works towards eliminating
timekeeping_delta_to_ns() in favour of timekeeping_cycles_to_ns().

No functional change.

Suggested-by: Thomas Gleixner 
Signed-off-by: Adrian Hunter 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20240325064023.2997-14-adrian.hunter@intel.com

timekeeping: Reuse timekeeping_cycles_to_ns()

2024-04-08T13:03:07+00:00

Simplify __timekeeping_get_ns() by reusing timekeeping_cycles_to_ns().

No functional change.

Suggested-by: Thomas Gleixner 
Signed-off-by: Adrian Hunter 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20240325064023.2997-13-adrian.hunter@intel.com

timekeeping: Tidy timekeeping_cycles_to_ns() slightly

2024-04-08T13:03:07+00:00

Put together declaration and initialization of the local variable 'delta'.

Suggested-by: Thomas Gleixner 
Signed-off-by: Adrian Hunter 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20240325064023.2997-12-adrian.hunter@intel.com

timekeeping: Rename fast_tk_get_delta_ns() to __timekeeping_get_ns()

2024-04-08T13:03:07+00:00

Rename fast_tk_get_delta_ns() to __timekeeping_get_ns() to prepare for its
reuse as a general timekeeping helper function.

Suggested-by: Thomas Gleixner 
Signed-off-by: Adrian Hunter 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20240325064023.2997-11-adrian.hunter@intel.com