Linux Ethernet Bridging - Nov 2022 - [Bridge] [RFC][PATCH v3 00/33] timers: Use timer_shutdown*() before freeing timers

On Fri, Nov 04, 2022 at 01:40:53AM -0400, Steven Rostedt
wrote:
> 
> Back in April, I posted an RFC patch set to help mitigate a common issue
> where a timer gets armed just before it is freed, and when the timer
> goes off, it crashes in the timer code without any evidence of who the
> culprit was. I got side tracked and never finished up on that patch set.
> Since this type of crash is still our #1 crash we are seeing in the field,
> it has become a priority again to finish it.
> 
> This is v3 of that patch set. Thomas Gleixner posted an untested version
> that makes timer->function NULL as the flag that it is shutdown. I took
that
> code, tested it (fixed it up), added more comments, and changed the
> name to timer_shutdown_sync(). I also converted it to use WARN_ON_ONCE()
> instead of just WARN_ON() as Linus asked for.
> 
Unfortunately the renaming caused some symbol conflicts.

Global definition: timer_shutdown

  File             Line
0 time.c            93 static inline void timer_shutdown(struct
clock_event_device *evt)
1 arm_arch_timer.c 690 static __always_inline int timer_shutdown(const int
access,
2 timer-fttmr010.c 105 int (*timer_shutdown)(struct clock_event_device *evt);
3 timer-sp804.c    158 static inline void timer_shutdown(struct
clock_event_device *evt)
4 timer.h          239 static inline int timer_shutdown(struct timer_list
*timer)

Guenter

On Fri, 4 Nov 2022 12:22:32 -0700
Guenter Roeck <linux at roeck-us.net> wrote:
> Unfortunately the renaming caused some symbol conflicts.
> 
> Global definition: timer_shutdown
> 
>   File             Line
> 0 time.c            93 static inline void timer_shutdown(struct
clock_event_device *evt)
> 1 arm_arch_timer.c 690 static __always_inline int timer_shutdown(const int
access,
> 2 timer-fttmr010.c 105 int (*timer_shutdown)(struct clock_event_device
*evt);
> 3 timer-sp804.c    158 static inline void timer_shutdown(struct
clock_event_device *evt)
> 4 timer.h          239 static inline int timer_shutdown(struct timer_list
*timer)
$ git grep '\btimer_shutdown'
arch/arm/mach-spear/time.c:static inline void timer_shutdown(struct
clock_event_device *evt)
arch/arm/mach-spear/time.c:     timer_shutdown(evt);
arch/arm/mach-spear/time.c:     timer_shutdown(evt);
arch/arm/mach-spear/time.c:     timer_shutdown(evt);
drivers/clocksource/arm_arch_timer.c:static __always_inline int
timer_shutdown(const int access,
drivers/clocksource/arm_arch_timer.c:   return
timer_shutdown(ARCH_TIMER_VIRT_ACCESS, clk);
drivers/clocksource/arm_arch_timer.c:   return
timer_shutdown(ARCH_TIMER_PHYS_ACCESS, clk);
drivers/clocksource/arm_arch_timer.c:   return
timer_shutdown(ARCH_TIMER_MEM_VIRT_ACCESS, clk);
drivers/clocksource/arm_arch_timer.c:   return
timer_shutdown(ARCH_TIMER_MEM_PHYS_ACCESS, clk);
drivers/clocksource/timer-fttmr010.c:   int (*timer_shutdown)(struct
clock_event_device *evt);
drivers/clocksource/timer-fttmr010.c:   fttmr010->timer_shutdown(evt);
drivers/clocksource/timer-fttmr010.c:   fttmr010->timer_shutdown(evt);
drivers/clocksource/timer-fttmr010.c:   fttmr010->timer_shutdown(evt);
drivers/clocksource/timer-fttmr010.c:           fttmr010->timer_shutdown =
ast2600_timer_shutdown;
drivers/clocksource/timer-fttmr010.c:           fttmr010->timer_shutdown =
fttmr010_timer_shutdown;
drivers/clocksource/timer-fttmr010.c:   fttmr010->clkevt.set_state_shutdown =
fttmr010->timer_shutdown;
drivers/clocksource/timer-fttmr010.c:   fttmr010->clkevt.tick_resume =
fttmr010->timer_shutdown;
drivers/clocksource/timer-sp804.c:static inline void timer_shutdown(struct
clock_event_device *evt)
drivers/clocksource/timer-sp804.c:      timer_shutdown(evt);
drivers/clocksource/timer-sp804.c:      timer_shutdown(evt);

Honestly, I think these need to be renamed, as "timer_shutdown()"
should be specific to the timer code, and not individual timers.

I'll start making a patch set that starts by renaming these timers,
then adds the timer_shutdown() API, and finished with the trivial
updates, and that will be a real "PATCH" (non RFC).

Linus, should I also add any patches that has already been acked by the
respective maintainer?

-- Steve