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Date: Mon, 9 Jan 2023 15:13:06 +0800
From: genjian zhang <zhanggenjian123@...il.com>
To: paulmck@...nel.org
Cc: frederic@...nel.org, linux-kernel@...r.kernel.org,
Genjian Zhang <zhanggenjian@...inos.cn>,
k2ci <kernel-bot@...inos.cn>, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] context_tracking: Use arch_atomic_*() in __ct_user_enter
and __ct_user_exit
On Fri, Jan 6, 2023 at 10:53 PM Paul E. McKenney <paulmck@...nel.org> wrote:
>
> On Thu, Nov 10, 2022 at 04:24:43PM +0800, Genjian wrote:
> > From: Genjian Zhang <zhanggenjian@...inos.cn>
> >
> > vmlinux.o: warning: objtool: __ct_user_enter+0x45: call to
> > __kasan_check_write() leaves .noinstr.text section
> > vmlinux.o: warning: objtool: __ct_user_exit+0x3f: call to
> > __kasan_check_write() leaves .noinstr.text section
> >
> > noinstr cannot have atomic_*() functions.because they have explicit
> > instrumentation.Switch to arch_ prefixed atomic operation functions to
> > avoid the explicit instrumentation.
> >
> > Reported-by: k2ci <kernel-bot@...inos.cn>
> > Reported-by: kernel test robot <lkp@...el.com>
> > Signed-off-by: Genjian Zhang <zhanggenjian@...inos.cn>
>
> Apologies for the delay, but finally queued, thank you! Frederic gave
> his ack off-list, which I have included in the wordsmithed version below.
> Could you please check to make sure that I did not mess anything up?
>
> Thanx, Paul
>
> ------------------------------------------------------------------------
>
> commit 936acd859f4a7b2b0f9900e26bc972385286df6e
> Author: Genjian Zhang <zhanggenjian@...inos.cn>
> Date: Thu Nov 10 16:24:43 2022 +0800
>
> context_tracking: Use arch_atomic_*() in __ct_user_enter and __ct_user_exit
>
> The following diagnostics are issued by objtool:
>
> vmlinux.o: warning: objtool: __ct_user_enter+0x45: call to
> __kasan_check_write() leaves .noinstr.text section
> vmlinux.o: warning: objtool: __ct_user_exit+0x3f: call to
> __kasan_check_write() leaves .noinstr.text section
>
> The reason for these diagnostics is that code marked noinstr if prohibited
> from using atomic_*() functions, which have explicit instrumentation.
> Therefore, switch to arch_ prefixed atomic operation functions to avoid
> the explicit instrumentation.
>
> Reported-by: k2ci <kernel-bot@...inos.cn>
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Genjian Zhang <zhanggenjian@...inos.cn>
> Acked-by: Frederic Weisbecker <frederic@...nel.org>
> Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
>
> diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
> index 77978e3723771..a09f1c19336ae 100644
> --- a/kernel/context_tracking.c
> +++ b/kernel/context_tracking.c
> @@ -510,7 +510,7 @@ void noinstr __ct_user_enter(enum ctx_state state)
> * In this we case we don't care about any concurrency/ordering.
> */
> if (!IS_ENABLED(CONFIG_CONTEXT_TRACKING_IDLE))
> - atomic_set(&ct->state, state);
> + arch_atomic_set(&ct->state, state);
> } else {
> /*
> * Even if context tracking is disabled on this CPU, because it's outside
> @@ -527,7 +527,7 @@ void noinstr __ct_user_enter(enum ctx_state state)
> */
> if (!IS_ENABLED(CONFIG_CONTEXT_TRACKING_IDLE)) {
> /* Tracking for vtime only, no concurrent RCU EQS accounting */
> - atomic_set(&ct->state, state);
> + arch_atomic_set(&ct->state, state);
> } else {
> /*
> * Tracking for vtime and RCU EQS. Make sure we don't race
> @@ -535,7 +535,7 @@ void noinstr __ct_user_enter(enum ctx_state state)
> * RCU only requires RCU_DYNTICKS_IDX increments to be fully
> * ordered.
> */
> - atomic_add(state, &ct->state);
> + arch_atomic_add(state, &ct->state);
> }
> }
> }
> @@ -630,12 +630,12 @@ void noinstr __ct_user_exit(enum ctx_state state)
> * In this we case we don't care about any concurrency/ordering.
> */
> if (!IS_ENABLED(CONFIG_CONTEXT_TRACKING_IDLE))
> - atomic_set(&ct->state, CONTEXT_KERNEL);
> + arch_atomic_set(&ct->state, CONTEXT_KERNEL);
>
> } else {
> if (!IS_ENABLED(CONFIG_CONTEXT_TRACKING_IDLE)) {
> /* Tracking for vtime only, no concurrent RCU EQS accounting */
> - atomic_set(&ct->state, CONTEXT_KERNEL);
> + arch_atomic_set(&ct->state, CONTEXT_KERNEL);
> } else {
> /*
> * Tracking for vtime and RCU EQS. Make sure we don't race
> @@ -643,7 +643,7 @@ void noinstr __ct_user_exit(enum ctx_state state)
> * RCU only requires RCU_DYNTICKS_IDX increments to be fully
> * ordered.
> */
> - atomic_sub(state, &ct->state);
> + arch_atomic_sub(state, &ct->state);
> }
> }
> }
Seems good to me.
Thanks,
Genjian.
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