[ Upstream commit d0304569fb019d1bcfbbbce1ce6df6b96f04079b ] 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 clocksource_cyc2ns() calculation will eventually overflow. Add protection against that. Simplify by folding together clocksource_delta() and clocksource_cyc2ns() into cycles_to_nsec_safe(). Check against max_cycles, falling back to a slower higher precision calculation. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20240325064023.2997-20-adrian.hunter@intel.com Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 07c54cc5988f19c9642fd463c2dbdac7fc52f777 upstream.
After the recent commit 5097cbcb38e6 ("sched/isolation: Prevent boot crash
when the boot CPU is nohz_full") the kernel no longer crashes, but there is
another problem.
In this case tick_setup_device() calls tick_take_do_timer_from_boot() to
update tick_do_timer_cpu and this triggers the WARN_ON_ONCE(irqs_disabled)
in smp_call_function_single().
Kill tick_take_do_timer_from_boot() and just use WRITE_ONCE(), the new
comment explains why this is safe (thanks Thomas!).
Fixes: 08ae95f4fd3b ("nohz_full: Allow the boot CPU to be nohz_full")
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240528122019.GA28794@redhat.com
Link: https://lore.kernel.org/all/20240522151742.GA10400@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When tmigr_setup_groups() fails the level 0 group allocation, then the
cleanup derefences index -1 of the local stack array.
Prevent this by checking the loop condition first.
Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Link: https://lore.kernel.org/r/20240506041059.86877-1-ppbuk5246@gmail.com
tick_do_timer_cpu is used lockless to check which CPU needs to take care of the per tick timekeeping duty. This is done to avoid a thundering herd problem on jiffies_lock. The read and writes are not annotated so KCSAN complains about data races: BUG: KCSAN: data-race in tick_nohz_idle_stop_tick / tick_nohz_next_event write to 0xffffffff8a2bda30 of 4 bytes by task 0 on cpu 26: tick_nohz_idle_stop_tick+0x3b1/0x4a0 do_idle+0x1e3/0x250 read to 0xffffffff8a2bda30 of 4 bytes by task 0 on cpu 16: tick_nohz_next_event+0xe7/0x1e0 tick_nohz_get_sleep_length+0xa7/0xe0 menu_select+0x82/0xb90 cpuidle_select+0x44/0x60 do_idle+0x1c2/0x250 value changed: 0x0000001a -> 0xffffffff Annotate them with READ/WRITE_ONCE() to document the intentional data race. Reported-by: Mirsad Todorovac <mirsad.todorovac@alu.unizg.hr> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Tested-by: Sean Anderson <sean.anderson@seco.com> Link: https://lore.kernel.org/r/87cyqy7rt3.ffs@tglx
Commit 4b6f4c5a67c0 ("timer/migration: Remove buggy early return on
deactivation") removed the logic to return early in tmigr_update_events()
on deactivation. With this the problem with a not properly updated first
global event in a hierarchy containing only a single group was fixed.
But when having a look at this code path with a hierarchy with more than a
single level, now unnecessary work is done (example is partially copied
from the message of the commit mentioned above):
[GRP1:0]
migrator = GRP0:0
active = GRP0:0
nextevt = T0:0i, T0:1
/ \
[GRP0:0] [GRP0:1]
migrator = 0 migrator = NONE
active = 0 active = NONE
nextevt = T0i, T1 nextevt = T2
/ \ / \
0 (T0i) 1 (T1) 2 (T2) 3
active idle idle idle
0) CPU 0 is active thus its event is ignored (the letter 'i') and so are
upper levels' events. CPU 1 is idle and has the timer T1 enqueued.
CPU 2 also has a timer. The expiry order is T0 (ignored) < T1 < T2
[GRP1:0]
migrator = GRP0:0
active = GRP0:0
nextevt = T0:0i, T0:1
/ \
[GRP0:0] [GRP0:1]
migrator = NONE migrator = NONE
active = NONE active = NONE
nextevt = T1 nextevt = T2
/ \ / \
0 (T0i) 1 (T1) 2 (T2) 3
idle idle idle idle
1) CPU 0 goes idle without global event queued. Therefore KTIME_MAX is
pushed as its next expiry and its own event kept as "ignore". Without this
early return the following steps happen in tmigr_update_events() when
child = null and group = GRP0:0 :
lock(GRP0:0->lock);
timerqueue_del(GRP0:0, T0i);
unlock(GRP0:0->lock);
[GRP1:0]
migrator = NONE
active = NONE
nextevt = T0:0, T0:1
/ \
[GRP0:0] [GRP0:1]
migrator = NONE migrator = NONE
active = NONE active = NONE
nextevt = T1 nextevt = T2
/ \ / \
0 (T0i) 1 (T1) 2 (T2) 3
idle idle idle idle
2) The change now propagates up to the top. Then tmigr_update_events()
updates the group event of GRP0:0 and executes the following steps
(child = GRP0:0 and group = GRP0:0):
lock(GRP0:0->lock);
lock(GRP1:0->lock);
evt = tmigr_next_groupevt(GRP0:0); -> this removes the ignored events
in GRP0:0
... update GRP1:0 group event and timerqueue ...
unlock(GRP1:0->lock);
unlock(GRP0:0->lock);
So the dance in 1) with locking the GRP0:0->lock and removing the T0i from
the timerqueue is redundand as this is done nevertheless in 2) when
tmigr_next_groupevt(GRP0:0) is executed.
Revert commit 4b6f4c5a67c0 ("timer/migration: Remove buggy early return on
deactivation") and add a condition into return path to skip the return
only, when hierarchy contains a single group. Adapt comments accordingly.
Fixes: 4b6f4c5a67c0 ("timer/migration: Remove buggy early return on deactivation")
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/87cyr49on2.fsf@somnus
When a group event is updated with its expiry unchanged but a different
CPU, that target change may go unnoticed and the event may be propagated
up with a stale CPU value. The following depicts a scenario that has
been actually observed:
[GRP2:0]
migrator = GRP1:1
active = GRP1:1
nextevt = TGRP1:0 (T0)
/ \
[GRP1:0] [GRP1:1]
migrator = NONE [...]
active = NONE
nextevt = TGRP0:0 (T0)
/ \
[GRP0:0] [...]
migrator = NONE
active = NONE
nextevt = T0
/ \
0 (T0) 1 (T1)
idle idle
0) The hierarchy has 3 levels. The left part (GRP1:0) is all idle,
including CPU 0 and CPU 1 which have a timer each: T0 and T1. They have
the same expiry value.
[GRP2:0]
migrator = GRP1:1
active = GRP1:1
nextevt = KTIME_MAX
/ \
[GRP1:0] [GRP1:1]
migrator = NONE [...]
active = NONE
nextevt = TGRP0:0 (T0)
/ \
[GRP0:0] [...]
migrator = NONE
active = NONE
nextevt = T0
/ \
0 (T0) 1 (T1)
idle idle
1) The migrator in GRP1:1 handles remotely T0. The event is dequeued
from the top and T0 executed.
[GRP2:0]
migrator = GRP1:1
active = GRP1:1
nextevt = KTIME_MAX
/ \
[GRP1:0] [GRP1:1]
migrator = NONE [...]
active = NONE
nextevt = TGRP0:0 (T0)
/ \
[GRP0:0] [...]
migrator = NONE
active = NONE
nextevt = T1
/ \
0 1 (T1)
idle idle
2) The migrator in GRP1:1 fetches the next timer for CPU 0 and finds
none. But it updates the events from its groups, starting with GRP0:0
which now has T1 as its next event. So far so good.
[GRP2:0]
migrator = GRP1:1
active = GRP1:1
nextevt = KTIME_MAX
/ \
[GRP1:0] [GRP1:1]
migrator = NONE [...]
active = NONE
nextevt = TGRP0:0 (T0)
/ \
[GRP0:0] [...]
migrator = NONE
active = NONE
nextevt = T1
/ \
0 1 (T1)
idle idle
3) The migrator in GRP1:1 proceeds upward and updates the events in
GRP1:0. The child event TGRP0:0 is found queued with the same expiry
as before. And therefore it is left unchanged. However the target CPU
is not the same but that fact is ignored so TGRP0:0 still points to
CPU 0 when it should point to CPU 1.
[GRP2:0]
migrator = GRP1:1
active = GRP1:1
nextevt = TGRP1:0 (T0)
/ \
[GRP1:0] [GRP1:1]
migrator = NONE [...]
active = NONE
nextevt = TGRP0:0 (T0)
/ \
[GRP0:0] [...]
migrator = NONE
active = NONE
nextevt = T1
/ \
0 1 (T1)
idle idle
4) The propagation has reached the top level and TGRP1:0, having TGRP0:0
as its first event, also wrongly points to CPU 0. TGRP1:0 is added to
the top level group.
[GRP2:0]
migrator = GRP1:1
active = GRP1:1
nextevt = KTIME_MAX
/ \
[GRP1:0] [GRP1:1]
migrator = NONE [...]
active = NONE
nextevt = TGRP0:0 (T0)
/ \
[GRP0:0] [...]
migrator = NONE
active = NONE
nextevt = T1
/ \
0 1 (T1)
idle idle
5) The migrator in GRP1:1 dequeues the next event in top level pointing
to CPU 0. But since it actually doesn't see any real event in CPU 0, it
early returns.
6) T1 is left unhandled until either CPU 0 or CPU 1 wake up.
Some other bad scenario may involve trees with just two levels.
Fix this with unconditionally updating the CPU of the child event before
considering to early return while updating a queued event with an
unchanged expiry value.
Fixes: 7ee988770326 ("timers: Implement the hierarchical pull model")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Link: https://lore.kernel.org/r/Zg2Ct6M2RJAYHgCB@localhost.localdomain
Fix some text for consistency: s/lvl/level/ in a comment and use correct/full function names in comments. Correct spelling errors as reported by codespell. Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20240331172652.14086-7-rdunlap@infradead.org
Fix kernel-doc warnings in struct tick_sched: tick-sched.h:103: warning: Function parameter or struct member 'idle_sleeptime_seq' not described in 'tick_sched' tick-sched.h:104: warning: Excess struct member 'nohz_mode' description in 'tick_sched' Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20240331172652.14086-6-rdunlap@infradead.org
Fix a slew of kernel-doc warnings in tick-sched.c: tick-sched.c:650: warning: Function parameter or struct member 'now' not described in 'tick_nohz_update_jiffies' tick-sched.c:741: warning: No description found for return value of 'get_cpu_idle_time_us' tick-sched.c:767: warning: No description found for return value of 'get_cpu_iowait_time_us' tick-sched.c:1210: warning: No description found for return value of 'tick_nohz_idle_got_tick' tick-sched.c:1228: warning: No description found for return value of 'tick_nohz_get_next_hrtimer' tick-sched.c:1243: warning: No description found for return value of 'tick_nohz_get_sleep_length' tick-sched.c:1282: warning: Function parameter or struct member 'cpu' not described in 'tick_nohz_get_idle_calls_cpu' tick-sched.c:1282: warning: No description found for return value of 'tick_nohz_get_idle_calls_cpu' tick-sched.c:1294: warning: No description found for return value of 'tick_nohz_get_idle_calls' tick-sched.c:1577: warning: Function parameter or struct member 'hrtimer' not described in 'tick_setup_sched_timer' tick-sched.c:1577: warning: Excess function parameter 'mode' description in 'tick_setup_sched_timer' Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20240331172652.14086-5-rdunlap@infradead.org
If the clk ops.open() function returns an error, we don't release the
pccontext we allocated for this clock.
Re-organize the code slightly to make it all more obvious.
Reported-by: Rohit Keshri <rkeshri@redhat.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Fixes: 60c6946675fc ("posix-clock: introduce posix_clock_context concept")
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linuxfoundation.org>