On Wed, Jun 03, 2020 at 10:48:18AM +0200, Peter Zijlstra wrote:
> On Tue, Jun 02, 2020 at 09:38:53PM +0200, Peter Zijlstra wrote:
>
> > That said; noinstr's __no_sanitize combined with atomic_t might be
> > 'interesting', because the regular atomic things have explicit
> > annotations in them. That should give validation warnings for the right
> > .config, I'll have to go try -- so far I've made sure to never enable
> > the *SAN stuff.
>
> ---
> Subject: rcu: Fixup noinstr warnings
>
> A KCSAN build revealed we have explicit annoations through atomic_t
> usage, switch to arch_atomic_*() for the respective functions.
>
> vmlinux.o: warning: objtool: rcu_nmi_exit()+0x4d: call to
> __kcsan_check_access() leaves .noinstr.text section
> vmlinux.o: warning: objtool: rcu_dynticks_eqs_enter()+0x25: call to
> __kcsan_check_access() leaves .noinstr.text section
> vmlinux.o: warning: objtool: rcu_nmi_enter()+0x4f: call to
> __kcsan_check_access() leaves .noinstr.text section
> vmlinux.o: warning: objtool: rcu_dynticks_eqs_exit()+0x2a: call to
> __kcsan_check_access() leaves .noinstr.text section
> vmlinux.o: warning: objtool: __rcu_is_watching()+0x25: call to
> __kcsan_check_access() leaves .noinstr.text section
>
> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
This one does not apply cleanly onto the -rcu tree's "dev" branch, so
I am guessing that it is intended to be carried in -tip with yours and
Thomas's patch series.
If you do instead want this in -rcu, please let me know.
Thanx, Paul
> ---
> kernel/rcu/tree.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index c716eadc7617..162656b80db9 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -250,7 +250,7 @@ static noinstr void rcu_dynticks_eqs_enter(void)
> * next idle sojourn.
> */
> rcu_dynticks_task_trace_enter(); // Before ->dynticks update!
> - seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
> + seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
> // RCU is no longer watching. Better be in extended quiescent state!
> WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
> (seq & RCU_DYNTICK_CTRL_CTR));
> @@ -274,13 +274,13 @@ static noinstr void rcu_dynticks_eqs_exit(void)
> * and we also must force ordering with the next RCU read-side
> * critical section.
> */
> - seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
> + seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
> // RCU is now watching. Better not be in an extended quiescent state!
> rcu_dynticks_task_trace_exit(); // After ->dynticks update!
> WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
> !(seq & RCU_DYNTICK_CTRL_CTR));
> if (seq & RCU_DYNTICK_CTRL_MASK) {
> - atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks);
> + arch_atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks);
> smp_mb__after_atomic(); /* _exit after clearing mask. */
> }
> }
> @@ -313,7 +313,7 @@ static __always_inline bool
> rcu_dynticks_curr_cpu_in_eqs(void)
> {
> struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
>
> - return !(atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR);
> + return !(arch_atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR);
> }
>
> /*
> @@ -692,6 +692,7 @@ noinstr void rcu_nmi_exit(void)
> {
> struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
>
> + instrumentation_begin();
> /*
> * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
> * (We are exiting an NMI handler, so RCU better be paying attention
> @@ -705,7 +706,6 @@ noinstr void rcu_nmi_exit(void)
> * leave it in non-RCU-idle state.
> */
> if (rdp->dynticks_nmi_nesting != 1) {
> - instrumentation_begin();
> trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting,
> rdp->dynticks_nmi_nesting - 2,
> atomic_read(&rdp->dynticks));
> WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */
> @@ -714,7 +714,6 @@ noinstr void rcu_nmi_exit(void)
> return;
> }
>
> - instrumentation_begin();
> /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
> trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0,
> atomic_read(&rdp->dynticks));
> WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
