| Subject | Re: [patch V4 part 1 36/36] rcu: Make RCU IRQ enter/exit functions rely on in_nmi() | From | Alexandre Chartre <> | Date | Wed, 6 May 2020 19:09:27 +0200 |
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On 5/5/20 3:16 PM, Thomas Gleixner wrote: > From: Paul E. McKenney <paulmck@kernel.org> > > The rcu_nmi_enter_common() and rcu_nmi_exit_common() functions take an > "irq" parameter that indicates whether these functions are invoked from > an irq handler (irq==true) or an NMI handler (irq==false). However, > recent changes have applied notrace to a few critical functions such > that rcu_nmi_enter_common() and rcu_nmi_exit_common() many now rely > on in_nmi(). Note that in_nmi() works no differently than before, > but rather that tracing is now prohibited in code regions where in_nmi() > would incorrectly report NMI state. > > Therefore remove the "irq" parameter and inlines rcu_nmi_enter_common() and > rcu_nmi_exit_common() into rcu_nmi_enter() and rcu_nmi_exit(), > respectively. > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > --- > kernel/rcu/tree.c | 47 +++++++++++++++-------------------------------- > 1 file changed, 15 insertions(+), 32 deletions(-)
I already sent a RB for the first patches for this serie, and went through the remaining of them (20-36). I am not very familiar with some these areas so for what it's worth:
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
alex.
> --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -627,16 +627,18 @@ noinstr void rcu_user_enter(void) > } > #endif /* CONFIG_NO_HZ_FULL */ > > -/* > +/** > + * rcu_nmi_exit - inform RCU of exit from NMI context > + * > * If we are returning from the outermost NMI handler that interrupted an > * RCU-idle period, update rdp->dynticks and rdp->dynticks_nmi_nesting > * to let the RCU grace-period handling know that the CPU is back to > * being RCU-idle. > * > - * If you add or remove a call to rcu_nmi_exit_common(), be sure to test > + * If you add or remove a call to rcu_nmi_exit(), be sure to test > * with CONFIG_RCU_EQS_DEBUG=y. > */ > -static __always_inline void rcu_nmi_exit_common(bool irq) > +noinstr void rcu_nmi_exit(void) > { > struct rcu_data *rdp = this_cpu_ptr(&rcu_data); > > @@ -667,7 +669,7 @@ static __always_inline void rcu_nmi_exit > trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, atomic_read(&rdp->dynticks)); > WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */ > > - if (irq) > + if (!in_nmi()) > rcu_prepare_for_idle(); > instr_end(); > > @@ -675,22 +677,11 @@ static __always_inline void rcu_nmi_exit > rcu_dynticks_eqs_enter(); > // ... but is no longer watching here. > > - if (irq) > + if (!in_nmi()) > rcu_dynticks_task_enter(); > } > > /** > - * rcu_nmi_exit - inform RCU of exit from NMI context > - * > - * If you add or remove a call to rcu_nmi_exit(), be sure to test > - * with CONFIG_RCU_EQS_DEBUG=y. > - */ > -void noinstr rcu_nmi_exit(void) > -{ > - rcu_nmi_exit_common(false); > -} > - > -/** > * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle > * > * Exit from an interrupt handler, which might possibly result in entering > @@ -712,7 +703,7 @@ void noinstr rcu_nmi_exit(void) > void noinstr rcu_irq_exit(void) > { > lockdep_assert_irqs_disabled(); > - rcu_nmi_exit_common(true); > + rcu_nmi_exit(); > } > > /* > @@ -801,7 +792,7 @@ void noinstr rcu_user_exit(void) > #endif /* CONFIG_NO_HZ_FULL */ > > /** > - * rcu_nmi_enter_common - inform RCU of entry to NMI context > + * rcu_nmi_enter - inform RCU of entry to NMI context > * @irq: Is this call from rcu_irq_enter? > * > * If the CPU was idle from RCU's viewpoint, update rdp->dynticks and > @@ -810,10 +801,10 @@ void noinstr rcu_user_exit(void) > * long as the nesting level does not overflow an int. (You will probably > * run out of stack space first.) > * > - * If you add or remove a call to rcu_nmi_enter_common(), be sure to test > + * If you add or remove a call to rcu_nmi_enter(), be sure to test > * with CONFIG_RCU_EQS_DEBUG=y. > */ > -static __always_inline void rcu_nmi_enter_common(bool irq) > +noinstr void rcu_nmi_enter(void) > { > long incby = 2; > struct rcu_data *rdp = this_cpu_ptr(&rcu_data); > @@ -831,18 +822,18 @@ static __always_inline void rcu_nmi_ente > */ > if (rcu_dynticks_curr_cpu_in_eqs()) { > > - if (irq) > + if (!in_nmi()) > rcu_dynticks_task_exit(); > > // RCU is not watching here ... > rcu_dynticks_eqs_exit(); > // ... but is watching here. > > - if (irq) > + if (!in_nmi()) > rcu_cleanup_after_idle(); > > incby = 1; > - } else if (irq) { > + } else if (!in_nmi()) { > instr_begin(); > if (tick_nohz_full_cpu(rdp->cpu) && > rdp->dynticks_nmi_nesting == DYNTICK_IRQ_NONIDLE && > @@ -877,14 +868,6 @@ static __always_inline void rcu_nmi_ente > } > > /** > - * rcu_nmi_enter - inform RCU of entry to NMI context > - */ > -noinstr void rcu_nmi_enter(void) > -{ > - rcu_nmi_enter_common(false); > -} > - > -/** > * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle > * > * Enter an interrupt handler, which might possibly result in exiting > @@ -909,7 +892,7 @@ noinstr void rcu_nmi_enter(void) > noinstr void rcu_irq_enter(void) > { > lockdep_assert_irqs_disabled(); > - rcu_nmi_enter_common(true); > + rcu_nmi_enter(); > } > > /* >
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