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Date: Mon, 9 Jan 2023 07:10:55 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: genjian zhang <zhanggenjian123@...il.com>
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 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@...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.
Thank you for checking!
Thanx, Paul
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