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Date:   Mon, 9 Jan 2023 07:10:55 -0800
From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     genjian zhang <zhanggenjian123@gmail.com>
Cc:     frederic@kernel.org, linux-kernel@vger.kernel.org,
        Genjian Zhang <zhanggenjian@kylinos.cn>,
        k2ci <kernel-bot@kylinos.cn>, kernel test robot <lkp@intel.com>
Subject: Re: [PATCH] context_tracking: Use arch_atomic_*() in __ct_user_enter
 and __ct_user_exit
Message-ID: <20230109151055.GN4028633@paulmck-ThinkPad-P17-Gen-1>
Reply-To: paulmck@kernel.org
References: <20221110082443.4069161-1-zhanggenjian@kylinos.cn>
 <20230106145331.GS4028633@paulmck-ThinkPad-P17-Gen-1>
 <CAOd03ySSrC996R_=xxC4M7s=X-V-jC1D-5rTsixWorg_qQmTLA@mail.gmail.com>
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On Mon, Jan 09, 2023 at 03:13:06PM +0800, genjian zhang wrote:
> On Fri, Jan 6, 2023 at 10:53 PM Paul E. McKenney <paulmck@kernel.org> wrote:
> >
> > On Thu, Nov 10, 2022 at 04:24:43PM +0800, Genjian wrote:
> > > From: Genjian Zhang <zhanggenjian@kylinos.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@kylinos.cn>
> > > Reported-by: kernel test robot <lkp@intel.com>
> > > Signed-off-by: Genjian Zhang <zhanggenjian@kylinos.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@kylinos.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@kylinos.cn>
> >     Reported-by: kernel test robot <lkp@intel.com>
> >     Signed-off-by: Genjian Zhang <zhanggenjian@kylinos.cn>
> >     Acked-by: Frederic Weisbecker <frederic@kernel.org>
> >     Signed-off-by: Paul E. McKenney <paulmck@kernel.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.

Thank you for checking!

							Thanx, Paul