Re: [GIT pull] timers/cleanups for v7.3-rc1

[Nathan Chancellor <nathan@kernel.org>]

Hi Thomas,

On Mon, Aug 17, 2026 at 01:23:52PM +0200, Thomas Gleixner wrote:
>       calibrate: Rework delay timer calibration
...
> diff --git a/arch/arm/include/asm/timex.h b/arch/arm/include/asm/timex.h
> index 6d1337c169cd..94e40c19cfc5 100644
> --- a/arch/arm/include/asm/timex.h
> +++ b/arch/arm/include/asm/timex.h
> @@ -10,7 +10,10 @@
>  #define _ASMARM_TIMEX_H
>  
>  typedef unsigned long cycles_t;
> -#define get_cycles()	({ cycles_t c; read_current_timer(&c) ? 0 : c; })
> +// Temporary workaround until timex.h is cleaned up
> +bool delay_read_timer(unsigned long *t);
> +
> +#define get_cycles()	({ cycles_t c; delay_read_timer(&c) ? 0 : c; })
>  #define random_get_entropy() (((unsigned long)get_cycles()) ?: random_get_entropy_fallback())
>  
>  #endif
> diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c
> index b7fe84f68bf1..7e9304012a68 100644
> --- a/arch/arm/lib/delay.c
> +++ b/arch/arm/lib/delay.c
> @@ -12,7 +12,6 @@
>  #include <linux/init.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
> -#include <linux/timex.h>
>  
>  /*
>   * Default to the loop-based delay implementation.
> @@ -27,15 +26,14 @@ static const struct delay_timer *delay_timer;
>  static bool delay_calibrated;
>  static u64 delay_res;
>  
> -int read_current_timer(unsigned long *timer_val)
> +bool delay_read_timer(unsigned long *timer_val)
>  {
>  	if (!delay_timer)
> -		return -ENXIO;
> -
> +		return false;
>  	*timer_val = delay_timer->read_current_timer();
> -	return 0;
> +	return true;
>  }
> -EXPORT_SYMBOL_GPL(read_current_timer);
> +EXPORT_SYMBOL_GPL(delay_read_timer);
>  
>  static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift)
>  {

I bisected a hang that I see after getting to userspace when virtually
testing some ARM configurations to commit dfc256dac54c ("calibrate:
Rework delay timer calibration"). It looks like the branches in
get_cycles() were not updated for the changed meaning of the return of
delay_read_timer()? This appears to resolve it for me but I am not sure
if I am missing something.

diff --git a/arch/arm/include/asm/timex.h b/arch/arm/include/asm/timex.h
index 94e40c19cfc5..4d31eab9dba2 100644
--- a/arch/arm/include/asm/timex.h
+++ b/arch/arm/include/asm/timex.h
@@ -13,7 +13,7 @@ typedef unsigned long cycles_t;
 // Temporary workaround until timex.h is cleaned up
 bool delay_read_timer(unsigned long *t);
 
-#define get_cycles()	({ cycles_t c; delay_read_timer(&c) ? 0 : c; })
+#define get_cycles()	({ cycles_t c; delay_read_timer(&c) ? c : 0; })
 #define random_get_entropy() (((unsigned long)get_cycles()) ?: random_get_entropy_fallback())
 
 #endif
--

# bad: [f4cdf7ca9a1fdcca413157df19753f388a5a224e] Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
# good: [8d3ae59288f1e7d58d76558a6ee96d533bc5019f] Linux 7.2
git bisect start 'f4cdf7ca9a1fdcca413157df19753f388a5a224e' 'v7.2'
# bad: [cbe8aadf1551f3f4a853f24b3b96d9f0eea49c53] Merge tag 'soc-dt-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc
git bisect bad cbe8aadf1551f3f4a853f24b3b96d9f0eea49c53
# good: [762fffa407d8d24288513538cf5d17c2c5425258] Merge tag 'irq-core-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good 762fffa407d8d24288513538cf5d17c2c5425258
# good: [0b02b8f941911895775b56c428e01b117ce9d2f3] Merge tag 'spacemit-dt-for-7.3-1' of https://git.kernel.org/pub/scm/linux/kernel/git/spacemit/linux into soc/dt
git bisect good 0b02b8f941911895775b56c428e01b117ce9d2f3
# good: [f809cedd3f614e4596aae23756ed44085fee1691] Merge tag 'qcom-arm32-for-7.3' of https://git.kernel.org/pub/scm/linux/kernel/git/qcom/linux into soc/dt
git bisect good f809cedd3f614e4596aae23756ed44085fee1691
# bad: [3b4128b9f374b4219eb716f4ad8a307bc7eb3d84] Merge tag 'timers-core-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect bad 3b4128b9f374b4219eb716f4ad8a307bc7eb3d84
# bad: [030c9f813b8e48d2b066983c94cf6294968f9496] Merge tag 'timers-cleanups-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect bad 030c9f813b8e48d2b066983c94cf6294968f9496
# good: [8b5d31123f41957fe265deeb03ee87fe62f155a8] Merge tag 'irq-drivers-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good 8b5d31123f41957fe265deeb03ee87fe62f155a8
# good: [6c4a1b972643d72bd26f674677df8b5a6a3fe94f] selftests/futex: Provide thread creation and synchronization helpers
git bisect good 6c4a1b972643d72bd26f674677df8b5a6a3fe94f
# good: [66344732b058e75f7ef25dcd0fbb483f9c000633] smp: Remove preempt_disable() from smp_call_function()
git bisect good 66344732b058e75f7ef25dcd0fbb483f9c000633
# good: [0dd1a54f44348d9cf6bae57a2b5cb0b53826a2c7] Merge tag 'smp-core-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good 0dd1a54f44348d9cf6bae57a2b5cb0b53826a2c7
# good: [3ed403bbc967a3138b8e37566510e9b062751372] treewide: Remove CLOCK_TICK_RATE
git bisect good 3ed403bbc967a3138b8e37566510e9b062751372
# bad: [dfc256dac54c8b692110bf905c64cb130e15963d] calibrate: Rework delay timer calibration
git bisect bad dfc256dac54c8b692110bf905c64cb130e15963d
# first 'bad' commit: [dfc256dac54c8b692110bf905c64cb130e15963d] calibrate: Rework delay timer calibration

-- 
Cheers,
Nathan