Re: [tip: timers/core] time/jiffies: Register jiffies clocksource before usage

[Conor Dooley <conor@kernel.org>]

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On Tue, Jun 16, 2026 at 08:47:00PM +0200, Marek Szyprowski wrote:
> Dear All,
> 
> On 13.06.2026 15:28, tip-bot2 for Thomas Gleixner wrote:
> > The following commit has been merged into the timers/core branch of tip:
> >
> > Commit-ID:     f24df84cbe05e4471c04ac4b921fc0340bbc7752
> > Gitweb:        https://git.kernel.org/tip/f24df84cbe05e4471c04ac4b921fc0340bbc7752
> > Author:        Thomas Gleixner <tglx@kernel.org>
> > AuthorDate:    Tue, 09 Jun 2026 17:14:45 +02:00
> > Committer:     Thomas Gleixner <tglx@kernel.org>
> > CommitterDate: Sat, 13 Jun 2026 15:22:40 +02:00
> >
> > time/jiffies: Register jiffies clocksource before usage
> >
> > Teddy reported that a XEN HVM has a long boot delay, which was bisected to
> > the recent enhancements to the negative motion detection. It turned out
> > that the jiffies clocksource is used in early boot before it is registered,
> > which leaves the max_delta_raw field at zero. That causes the read out to
> > be clamped to the max delta of 0, which means time is not making progress.
> >
> > Cure it by ensuring that it is initialized before its first usage in
> > timekeeping_init().
> >
> > Fixes: 76031d9536a0 ("clocksource: Make negative motion detection more robust")
> > Reported-by: Teddy Astie <teddy.astie@vates.tech>
> > Signed-off-by: Thomas Gleixner <tglx@kernel.org>
> > Tested-by: Teddy Astie <teddy.astie@vates.tech>
> > Cc: stable@vger.kernel.org
> > Link: https://patch.msgid.link/87y0gn3fve.ffs@fw13
> > Closes: https://lore.kernel.org/all/1780914594.8631fc262581453bbf619ec5b2062170.19ea6c8227b000701b@vates.tech
> This patch landed recently in linux-next as commit f24df84cbe05 ("time/jiffies:
> Register jiffies clocksource before usage"). In my tests I found that it triggers
> the following warning on Qualcomm Robotics RB5 board
> (arch/arm64/boot/dts/qcom/qrb5165-rb5.dts):
> 
> clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
> 
> =============================
> [ BUG: Invalid wait context ]
> 7.1.0-rc1+ #16790 Not tainted
> -----------------------------
> swapper/0/0 is trying to lock:
> ffffb0d1364d1270 (clocksource_mutex){....}-{4:4}, at: __clocksource_register_scale+0x204/0x3e8
> other info that might help us debug this:
> context-{5:5}
> 1 lock held by swapper/0/0:
>  #0: ffffb0d1376855f0 (&tkd->lock){....}-{2:2}, at: timekeeping_init+0x13c/0x21c
> stack backtrace:
> CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.1.0-rc1+ #16790 PREEMPT
> Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT)
> Call trace:
>  show_stack+0x18/0x24 (C)
>  dump_stack_lvl+0x90/0xd0
>  dump_stack+0x18/0x24
>  __lock_acquire+0xa48/0x225c
>  lock_acquire+0x1c4/0x3f0
>  __mutex_lock+0xa8/0x8e4
>  mutex_lock_nested+0x24/0x30
>  __clocksource_register_scale+0x204/0x3e8
>  clocksource_default_clock+0x48/0x64
>  timekeeping_init+0x148/0x21c
>  start_kernel+0x4c8/0x8dc
>  __primary_switched+0x88/0x90
> arch_timer: cp15 timer running at 19.20MHz (virt).
> clocksource: arch_sys_counter: mask: 0xffffffffffffff max_cycles: 0x46d987e47, max_idle_ns: 440795202767 ns
> 
> 
> Reverting $subject on top of linux-next fixes this issue.

Same here:
    0.000000] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
[    0.000000]
[    0.000000] =============================
[    0.000000] [ BUG: Invalid wait context ]
[    0.000000] 7.1.0-06889-g4b99990cdf95 #1 Tainted: G        W
[    0.000000] -----------------------------
[    0.000000] swapper/0/0 is trying to lock:
[    0.000000] ffffffff820cd258 (clocksource_mutex){....}-{4:4}, at: __clocksource_register_scale+0x222/0x306
[    0.000000] other info that might help us debug this:
[    0.000000] context-{5:5}
[    0.000000] 1 lock held by swapper/0/0:
[    0.000000]  #0: ffffffff82fdae70 (&tkd->lock){....}-{2:2}, at: timekeeping_init+0x1a4/0x25e
[    0.000000] stack backtrace:
[    0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Tainted: G        W           7.1.0-06889-g4b99990cdf95 #1 PREEMPT_RT
[    0.000000] Tainted: [W]=WARN
[    0.000000] Hardware name: Microchip PolarFire-SoC Icicle Kit (DT)
[    0.000000] Call Trace:
[    0.000000] [<ffffffff8001c0e0>] dump_backtrace+0x1c/0x24
[    0.000000] [<ffffffff80002526>] show_stack+0x28/0x34
[    0.000000] [<ffffffff800135a0>] dump_stack_lvl+0x60/0x88
[    0.000000] [<ffffffff800135dc>] dump_stack+0x14/0x1c
[    0.000000] [<ffffffff800bb096>] __lock_acquire+0x81c/0x234e
[    0.000000] [<ffffffff800bd924>] lock_acquire+0x2e0/0x460
[    0.000000] [<ffffffff80d61d46>] mutex_lock_nested+0x44/0x8a
[    0.000000] [<ffffffff8012e704>] __clocksource_register_scale+0x222/0x306
[    0.000000] [<ffffffff80e15572>] clocksource_default_clock+0x48/0x62
[    0.000000] [<ffffffff80e15286>] timekeeping_init+0x1b6/0x25e
[    0.000000] [<ffffffff80e00f9c>] start_kernel+0x67c/0xc66
[    0.000000] clocksource: riscv_clocksource: mask: 0xffffffffffffffff max_cycles: 0x1d854df40, max_idle_ns: 3526361616960 ns

In your case, do you also see an increase in logging verbosity, as if
you had enabled debug on your commandline?

Cheers,
Conor.

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