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rcu: Make RCU IRQ enter/exit functions rely on in_nmi() 

The rcu_nmi_enter_common() and rcu_nmi_exit_common() functions take an
"irq" parameter that indicates whether these functions have been 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 inline 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>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Link: https://lkml.kernel.org/r/20200505134101.617130349@linutronix.de
This commit is contained in:
Paul E. McKenney 2020-02-13 12:31:16 -08:00 committed by Thomas Gleixner
parent ff5c4f5cad
commit 9ea366f669
1 changed files with 15 additions and 32 deletions
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47
kernel/rcu/tree.c
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@ -664,16 +664,18 @@ 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);
@ -704,7 +706,7 @@ static __always_inline void rcu_nmi_exit_common(bool irq)
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();
instrumentation_end();
@ -712,21 +714,10 @@ static __always_inline void rcu_nmi_exit_common(bool irq)
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
*
@ -749,7 +740,7 @@ void noinstr rcu_nmi_exit(void)
void noinstr rcu_irq_exit(void)
{
lockdep_assert_irqs_disabled();
rcu_nmi_exit_common(true);
rcu_nmi_exit();
}
/*
@ -838,7 +829,7 @@ 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
@ -847,10 +838,10 @@ 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);
@ -868,18 +859,18 @@ static __always_inline void rcu_nmi_enter_common(bool irq)
*/
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()) {
instrumentation_begin();
if (tick_nohz_full_cpu(rdp->cpu) &&
rdp->dynticks_nmi_nesting == DYNTICK_IRQ_NONIDLE &&
@ -913,14 +904,6 @@ static __always_inline void rcu_nmi_enter_common(bool irq)
barrier();
}
/**
* 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
*
@ -946,7 +929,7 @@ noinstr void rcu_nmi_enter(void)
noinstr void rcu_irq_enter(void)
{
lockdep_assert_irqs_disabled();
rcu_nmi_enter_common(true);
rcu_nmi_enter();
}
/*