This code is unused and can be removed now. Revert was straightforward.
Tested with light rcutorture.
Link: http://lore.kernel.org/r/CALCETrWNPOOdTrFabTDd=H7+wc6xJ9rJceg6OL1S0rTV5pfSsA@mail.gmail.com
Suggested-by: Andy Lutomirski <[email protected]>
Signed-off-by: Joel Fernandes (Google) <[email protected]>
---
Only made some commit message changes in this since v1.
include/linux/rcutiny.h | 3 --
kernel/rcu/tree.c | 82 ++++++++++-------------------------------
2 files changed, 19 insertions(+), 66 deletions(-)
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index b7607e2667ae..b3f689711289 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -14,9 +14,6 @@
#include <asm/param.h> /* for HZ */
-/* Never flag non-existent other CPUs! */
-static inline bool rcu_eqs_special_set(int cpu) { return false; }
-
static inline unsigned long get_state_synchronize_rcu(void)
{
return 0;
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 68ebf0eb64c8..417dd00b9e87 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -69,20 +69,10 @@
/* Data structures. */
-/*
- * Steal a bit from the bottom of ->dynticks for idle entry/exit
- * control. Initially this is for TLB flushing.
- */
-#define RCU_DYNTICK_CTRL_MASK 0x1
-#define RCU_DYNTICK_CTRL_CTR (RCU_DYNTICK_CTRL_MASK + 1)
-#ifndef rcu_eqs_special_exit
-#define rcu_eqs_special_exit() do { } while (0)
-#endif
-
static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
.dynticks_nesting = 1,
.dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
- .dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR),
+ .dynticks = ATOMIC_INIT(1),
};
struct rcu_state rcu_state = {
.level = { &rcu_state.node[0] },
@@ -229,20 +219,15 @@ void rcu_softirq_qs(void)
static void rcu_dynticks_eqs_enter(void)
{
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- int seq;
+ int special;
/*
- * CPUs seeing atomic_add_return() must see prior RCU read-side
+ * CPUs seeing atomic_inc_return() must see prior RCU read-side
* critical sections, and we also must force ordering with the
* next idle sojourn.
*/
- seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
- /* Better be in an extended quiescent state! */
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- (seq & RCU_DYNTICK_CTRL_CTR));
- /* Better not have special action (TLB flush) pending! */
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- (seq & RCU_DYNTICK_CTRL_MASK));
+ special = atomic_inc_return(&rdp->dynticks);
+ WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && special & 0x1);
}
/*
@@ -252,22 +237,15 @@ static void rcu_dynticks_eqs_enter(void)
static void rcu_dynticks_eqs_exit(void)
{
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- int seq;
+ int special;
/*
- * CPUs seeing atomic_add_return() must see prior idle sojourns,
+ * CPUs seeing atomic_inc_return() must see prior idle sojourns,
* and we also must force ordering with the next RCU read-side
* critical section.
*/
- seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
- 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);
- smp_mb__after_atomic(); /* _exit after clearing mask. */
- /* Prefer duplicate flushes to losing a flush. */
- rcu_eqs_special_exit();
- }
+ special = atomic_inc_return(&rdp->dynticks);
+ WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !(special & 0x1));
}
/*
@@ -284,9 +262,9 @@ static void rcu_dynticks_eqs_online(void)
{
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- if (atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR)
+ if (atomic_read(&rdp->dynticks) & 0x1)
return;
- atomic_add(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
+ atomic_add(0x1, &rdp->dynticks);
}
/*
@@ -298,7 +276,7 @@ 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 !(atomic_read(&rdp->dynticks) & 0x1);
}
/*
@@ -309,7 +287,7 @@ int rcu_dynticks_snap(struct rcu_data *rdp)
{
int snap = atomic_add_return(0, &rdp->dynticks);
- return snap & ~RCU_DYNTICK_CTRL_MASK;
+ return snap;
}
/*
@@ -318,7 +296,7 @@ int rcu_dynticks_snap(struct rcu_data *rdp)
*/
static bool rcu_dynticks_in_eqs(int snap)
{
- return !(snap & RCU_DYNTICK_CTRL_CTR);
+ return !(snap & 0x1);
}
/*
@@ -331,28 +309,6 @@ static bool rcu_dynticks_in_eqs_since(struct rcu_data *rdp, int snap)
return snap != rcu_dynticks_snap(rdp);
}
-/*
- * Set the special (bottom) bit of the specified CPU so that it
- * will take special action (such as flushing its TLB) on the
- * next exit from an extended quiescent state. Returns true if
- * the bit was successfully set, or false if the CPU was not in
- * an extended quiescent state.
- */
-bool rcu_eqs_special_set(int cpu)
-{
- int old;
- int new;
- struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
-
- do {
- old = atomic_read(&rdp->dynticks);
- if (old & RCU_DYNTICK_CTRL_CTR)
- return false;
- new = old | RCU_DYNTICK_CTRL_MASK;
- } while (atomic_cmpxchg(&rdp->dynticks, old, new) != old);
- return true;
-}
-
/*
* Let the RCU core know that this CPU has gone through the scheduler,
* which is a quiescent state. This is called when the need for a
@@ -366,13 +322,13 @@ bool rcu_eqs_special_set(int cpu)
*/
void rcu_momentary_dyntick_idle(void)
{
- int special;
+ struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+ int special = atomic_add_return(2, &rdp->dynticks);
- raw_cpu_write(rcu_data.rcu_need_heavy_qs, false);
- special = atomic_add_return(2 * RCU_DYNTICK_CTRL_CTR,
- &this_cpu_ptr(&rcu_data)->dynticks);
/* It is illegal to call this from idle state. */
- WARN_ON_ONCE(!(special & RCU_DYNTICK_CTRL_CTR));
+ WARN_ON_ONCE(!(special & 0x1));
+
+ raw_cpu_write(rcu_data.rcu_need_heavy_qs, false);
rcu_preempt_deferred_qs(current);
}
EXPORT_SYMBOL_GPL(rcu_momentary_dyntick_idle);
--
2.23.0.187.g17f5b7556c-goog
The dyntick-idle traces are a bit confusing. This patch makes it simpler
and adds some missing cases such as EQS-enter due to user vs idle mode.
Following are the changes:
(1) Add a new context field to trace_rcu_dyntick tracepoint. This
context field can be "USER", "IDLE" or "IRQ".
(2) Remove the "++=" and "--=" strings and replace them with
"StillNonIdle". This is much easier on the eyes, and the -- and ++
are easily apparent in the dynticks_nesting counters we are printing
anyway.
Signed-off-by: Joel Fernandes (Google) <[email protected]>
---
include/trace/events/rcu.h | 13 ++++++++-----
kernel/rcu/tree.c | 19 +++++++++++++------
2 files changed, 21 insertions(+), 11 deletions(-)
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 66122602bd08..474c1f7e7104 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -449,12 +449,14 @@ TRACE_EVENT_RCU(rcu_fqs,
*/
TRACE_EVENT_RCU(rcu_dyntick,
- TP_PROTO(const char *polarity, long oldnesting, long newnesting, atomic_t dynticks),
+ TP_PROTO(const char *polarity, const char *context, long oldnesting,
+ long newnesting, atomic_t dynticks),
- TP_ARGS(polarity, oldnesting, newnesting, dynticks),
+ TP_ARGS(polarity, context, oldnesting, newnesting, dynticks),
TP_STRUCT__entry(
__field(const char *, polarity)
+ __field(const char *, context)
__field(long, oldnesting)
__field(long, newnesting)
__field(int, dynticks)
@@ -462,14 +464,15 @@ TRACE_EVENT_RCU(rcu_dyntick,
TP_fast_assign(
__entry->polarity = polarity;
+ __entry->context = context;
__entry->oldnesting = oldnesting;
__entry->newnesting = newnesting;
__entry->dynticks = atomic_read(&dynticks);
),
- TP_printk("%s %lx %lx %#3x", __entry->polarity,
- __entry->oldnesting, __entry->newnesting,
- __entry->dynticks & 0xfff)
+ TP_printk("%s %s %lx %lx %#3x", __entry->polarity,
+ __entry->context, __entry->oldnesting, __entry->newnesting,
+ __entry->dynticks & 0xfff)
);
/*
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 417dd00b9e87..463407762b5a 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -533,7 +533,8 @@ static void rcu_eqs_enter(bool user)
}
lockdep_assert_irqs_disabled();
- trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, rdp->dynticks);
+ trace_rcu_dyntick(TPS("Start"), (user ? TPS("USER") : TPS("IDLE")),
+ rdp->dynticks_nesting, 0, rdp->dynticks);
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
rdp = this_cpu_ptr(&rcu_data);
do_nocb_deferred_wakeup(rdp);
@@ -606,14 +607,17 @@ static __always_inline void rcu_nmi_exit_common(bool irq)
* leave it in non-RCU-idle state.
*/
if (rdp->dynticks_nmi_nesting != 1) {
- trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, rdp->dynticks);
+ trace_rcu_dyntick(TPS("StillNonIdle"), TPS("IRQ"),
+ rdp->dynticks_nmi_nesting,
+ rdp->dynticks_nmi_nesting - 2, rdp->dynticks);
WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */
rdp->dynticks_nmi_nesting - 2);
return;
}
/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
- trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, rdp->dynticks);
+ trace_rcu_dyntick(TPS("Start"), TPS("IRQ"), rdp->dynticks_nmi_nesting,
+ 0, rdp->dynticks);
WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
if (irq)
@@ -700,7 +704,8 @@ static void rcu_eqs_exit(bool user)
rcu_dynticks_task_exit();
rcu_dynticks_eqs_exit();
rcu_cleanup_after_idle();
- trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, rdp->dynticks);
+ trace_rcu_dyntick(TPS("End"), (user ? TPS("USER") : TPS("IDLE")),
+ rdp->dynticks_nesting, 1, rdp->dynticks);
WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
WRITE_ONCE(rdp->dynticks_nesting, 1);
WARN_ON_ONCE(rdp->dynticks_nmi_nesting);
@@ -787,9 +792,11 @@ static __always_inline void rcu_nmi_enter_common(bool irq)
rdp->rcu_forced_tick = true;
tick_dep_set_cpu(rdp->cpu, TICK_DEP_BIT_RCU);
}
- trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
- rdp->dynticks_nmi_nesting,
+
+ trace_rcu_dyntick(incby == 1 ? TPS("End") : TPS("StillNonIdle"),
+ TPS("IRQ"), rdp->dynticks_nmi_nesting,
rdp->dynticks_nmi_nesting + incby, rdp->dynticks);
+
WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */
rdp->dynticks_nmi_nesting + incby);
barrier();
--
2.23.0.187.g17f5b7556c-goog