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Subject[PATCH 1/2] Markers Implementation for RCU Preempt Tracing - Ver II
This patch converts Preempt RCU Tracing code infrastructure to implement
markers.

- The rcupreempt_trace structure has been moved to the tracing
infrastructure and de-linked from the rcupreempt.c code. A per-cpu
instance of rcupreempt_trace structure will be maintained in
rcupreempt_trace.c

- The above change also renders a few macro definitions unused (such as
RCU_TRACE_CPU, RCU_TRACE_ME and RCU_TRACE_RDP) which have been
removed.

- Some of the helper functions in rcupreempt.c which were exported only
when CONFIG_RCU_TRACE was set are now exported unconditionally. These
functions operate on per-cpu variables that are used both by the RCU
and RCU Tracing code. The changes help in making RCU Tracing code
operate as a kernel module also.

- The references to rcupreempt-boost tracing in the module
initialisation and cleanup have been removed here to enable kernel
build, but will be brought in after enclosing them inside a #ifdef
CONFIG_PREEMPT_RCU_BOOST.

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
---
include/linux/rcupreempt.h | 10 ----
include/linux/rcupreempt_trace.h | 50 ++++++++++++------------
kernel/Kconfig.preempt | 7 +--
kernel/rcupreempt.c | 77 ++++++++++----------------------------
kernel/rcupreempt_trace.c | 79 +++++++++++++++++++++++++++++++++++++--
5 files changed, 125 insertions(+), 98 deletions(-)
Index: linux-2.6.24-rc5-rt1.RCU_MARKERS/include/linux/rcupreempt.h
===================================================================
--- linux-2.6.24-rc5-rt1.RCU_MARKERS.orig/include/linux/rcupreempt.h
+++ linux-2.6.24-rc5-rt1.RCU_MARKERS/include/linux/rcupreempt.h
@@ -96,16 +96,6 @@ extern int rcu_pending_rt(int cpu);
struct softirq_action;
extern void rcu_process_callbacks_rt(struct softirq_action *unused);

-#ifdef CONFIG_RCU_TRACE
-struct rcupreempt_trace;
-extern int *rcupreempt_flipctr(int cpu);
-extern long rcupreempt_data_completed(void);
-extern int rcupreempt_flip_flag(int cpu);
-extern int rcupreempt_mb_flag(int cpu);
-extern char *rcupreempt_try_flip_state_name(void);
-extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu);
-#endif
-
struct softirq_action;

#ifdef CONFIG_NO_HZ
Index: linux-2.6.24-rc5-rt1.RCU_MARKERS/include/linux/rcupreempt_trace.h
===================================================================
--- linux-2.6.24-rc5-rt1.RCU_MARKERS.orig/include/linux/rcupreempt_trace.h
+++ linux-2.6.24-rc5-rt1.RCU_MARKERS/include/linux/rcupreempt_trace.h
@@ -69,32 +69,32 @@ struct rcupreempt_trace {
long rcu_try_flip_m2;
};

-#ifdef CONFIG_RCU_TRACE
-#define RCU_TRACE(fn, arg) fn(arg);
-#else
-#define RCU_TRACE(fn, arg)
-#endif
+struct rcupreempt_probe_data {
+ const char *name;
+ const char *format;
+ marker_probe_func *probe_func;
+};
+
+#define DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_worker) \
+void rcupreempt_trace_worker##_callback(const struct marker *mdata, \
+ void *private_data, const char *format, ...) \
+{ \
+ struct rcupreempt_trace *trace; \
+ trace = (&per_cpu(trace_data, smp_processor_id())); \
+ rcupreempt_trace_worker(trace); \
+}
+
+#define INIT_RCUPREEMPT_PROBE(rcupreempt_trace_worker) \
+{ \
+ .name = __stringify(rcupreempt_trace_worker), \
+ .probe_func = rcupreempt_trace_worker##_callback \
+}

-extern void rcupreempt_trace_move2done(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_move2wait(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_1(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_e1(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_i1(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_ie1(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_g1(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_a1(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_ae1(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_a2(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_z1(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_ze1(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_z2(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_m1(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_me1(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_try_flip_m2(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_check_callbacks(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_done_remove(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_invoke(struct rcupreempt_trace *trace);
-extern void rcupreempt_trace_next_add(struct rcupreempt_trace *trace);
+extern int *rcupreempt_flipctr(int cpu);
+extern long rcupreempt_data_completed(void);
+extern int rcupreempt_flip_flag(int cpu);
+extern int rcupreempt_mb_flag(int cpu);
+extern char *rcupreempt_try_flip_state_name(void);

#endif /* __KERNEL__ */
#endif /* __LINUX_RCUPREEMPT_TRACE_H */
Index: linux-2.6.24-rc5-rt1.RCU_MARKERS/kernel/rcupreempt.c
===================================================================
--- linux-2.6.24-rc5-rt1.RCU_MARKERS.orig/kernel/rcupreempt.c
+++ linux-2.6.24-rc5-rt1.RCU_MARKERS/kernel/rcupreempt.c
@@ -54,7 +54,6 @@
#include <linux/delay.h>
#include <linux/byteorder/swabb.h>
#include <linux/cpumask.h>
-#include <linux/rcupreempt_trace.h>

/*
* PREEMPT_RCU data structures.
@@ -71,9 +70,6 @@ struct rcu_data {
struct rcu_head **waittail[GP_STAGES];
struct rcu_head *donelist;
struct rcu_head **donetail;
-#ifdef CONFIG_RCU_TRACE
- struct rcupreempt_trace trace;
-#endif /* #ifdef CONFIG_RCU_TRACE */
};
struct rcu_ctrlblk {
raw_spinlock_t fliplock; /* Protect state-machine transitions. */
@@ -97,10 +93,8 @@ enum rcu_try_flip_states {
rcu_try_flip_waitmb_state /* "M" */
};
static enum rcu_try_flip_states rcu_try_flip_state = rcu_try_flip_idle_state;
-#ifdef CONFIG_RCU_TRACE
static char *rcu_try_flip_state_names[] =
{ "idle", "waitack", "waitzero", "waitmb" };
-#endif /* #ifdef CONFIG_RCU_TRACE */

/*
* Enum and per-CPU flag to determine when each CPU has seen
@@ -147,24 +141,6 @@ static cpumask_t rcu_cpu_online_map = CP
#define RCU_DATA_CPU(cpu) (&per_cpu(rcu_data, cpu))

/*
- * Helper macro for tracing when the appropriate rcu_data is not
- * cached in a local variable, but where the CPU number is so cached.
- */
-#define RCU_TRACE_CPU(f, cpu) RCU_TRACE(f, &(RCU_DATA_CPU(cpu)->trace));
-
-/*
- * Helper macro for tracing when the appropriate rcu_data is not
- * cached in a local variable.
- */
-#define RCU_TRACE_ME(f) RCU_TRACE(f, &(RCU_DATA_ME()->trace));
-
-/*
- * Helper macro for tracing when the appropriate rcu_data is pointed
- * to by a local variable.
- */
-#define RCU_TRACE_RDP(f, rdp) RCU_TRACE(f, &((rdp)->trace));
-
-/*
* Return the number of RCU batches processed thus far. Useful
* for debug and statistics.
*/
@@ -332,7 +308,7 @@ static void __rcu_advance_callbacks(stru
if (rdp->waitlist[GP_STAGES - 1] != NULL) {
*rdp->donetail = rdp->waitlist[GP_STAGES - 1];
rdp->donetail = rdp->waittail[GP_STAGES - 1];
- RCU_TRACE_RDP(rcupreempt_trace_move2done, rdp);
+ trace_mark(rcupreempt_trace_move2done, "NULL");
}
for (i = GP_STAGES - 2; i >= 0; i--) {
if (rdp->waitlist[i] != NULL) {
@@ -351,7 +327,7 @@ static void __rcu_advance_callbacks(stru
wlc++;
rdp->nextlist = NULL;
rdp->nexttail = &rdp->nextlist;
- RCU_TRACE_RDP(rcupreempt_trace_move2wait, rdp);
+ trace_mark(rcupreempt_trace_move2wait, "NULL");
} else {
rdp->waitlist[0] = NULL;
rdp->waittail[0] = &rdp->waitlist[0];
@@ -595,9 +571,9 @@ rcu_try_flip_idle(void)
{
int cpu;

- RCU_TRACE_ME(rcupreempt_trace_try_flip_i1);
+ trace_mark(rcupreempt_trace_try_flip_i1, "NULL");
if (!rcu_pending(smp_processor_id())) {
- RCU_TRACE_ME(rcupreempt_trace_try_flip_ie1);
+ trace_mark(rcupreempt_trace_try_flip_ie1, "NULL");
return 0;
}

@@ -605,7 +581,7 @@ rcu_try_flip_idle(void)
* Do the flip.
*/

- RCU_TRACE_ME(rcupreempt_trace_try_flip_g1);
+ trace_mark(rcupreempt_trace_try_flip_g1, "NULL");
rcu_ctrlblk.completed++; /* stands in for rcu_try_flip_g2 */

/*
@@ -635,11 +611,11 @@ rcu_try_flip_waitack(void)
{
int cpu;

- RCU_TRACE_ME(rcupreempt_trace_try_flip_a1);
+ trace_mark(rcupreempt_trace_try_flip_a1, "NULL");
for_each_cpu_mask(cpu, rcu_cpu_online_map)
if (rcu_try_flip_waitack_needed(cpu) &&
per_cpu(rcu_flip_flag, cpu) != rcu_flip_seen) {
- RCU_TRACE_ME(rcupreempt_trace_try_flip_ae1);
+ trace_mark(rcupreempt_trace_try_flip_ae1, "NULL");
return 0;
}

@@ -649,7 +625,7 @@ rcu_try_flip_waitack(void)
*/

smp_mb(); /* see above block comment. */
- RCU_TRACE_ME(rcupreempt_trace_try_flip_a2);
+ trace_mark(rcupreempt_trace_try_flip_a2, "NULL");
return 1;
}

@@ -667,11 +643,11 @@ rcu_try_flip_waitzero(void)

/* Check to see if the sum of the "last" counters is zero. */

- RCU_TRACE_ME(rcupreempt_trace_try_flip_z1);
+ trace_mark(rcupreempt_trace_try_flip_z1, "NULL");
for_each_possible_cpu(cpu)
sum += per_cpu(rcu_flipctr, cpu)[lastidx];
if (sum != 0) {
- RCU_TRACE_ME(rcupreempt_trace_try_flip_ze1);
+ trace_mark(rcupreempt_trace_try_flip_ze1, "NULL");
return 0;
}

@@ -684,7 +660,7 @@ rcu_try_flip_waitzero(void)
dyntick_save_progress_counter(cpu);
}

- RCU_TRACE_ME(rcupreempt_trace_try_flip_z2);
+ trace_mark(rcupreempt_trace_try_flip_z2, "NULL");
return 1;
}

@@ -698,16 +674,16 @@ rcu_try_flip_waitmb(void)
{
int cpu;

- RCU_TRACE_ME(rcupreempt_trace_try_flip_m1);
+ trace_mark(rcupreempt_trace_try_flip_m1, "NULL");
for_each_cpu_mask(cpu, rcu_cpu_online_map)
if (rcu_try_flip_waitmb_needed(cpu) &&
per_cpu(rcu_mb_flag, cpu) != rcu_mb_done) {
- RCU_TRACE_ME(rcupreempt_trace_try_flip_me1);
+ trace_mark(rcupreempt_trace_try_flip_me1, "NULL");
return 0;
}

smp_mb(); /* Ensure that the above checks precede any following flip. */
- RCU_TRACE_ME(rcupreempt_trace_try_flip_m2);
+ trace_mark(rcupreempt_trace_try_flip_m2, "NULL");
return 1;
}

@@ -724,9 +700,9 @@ static void rcu_try_flip(void)
{
unsigned long oldirq;

- RCU_TRACE_ME(rcupreempt_trace_try_flip_1);
+ trace_mark(rcupreempt_trace_try_flip_1, "NULL");
if (unlikely(!spin_trylock_irqsave(&rcu_ctrlblk.fliplock, oldirq))) {
- RCU_TRACE_ME(rcupreempt_trace_try_flip_e1);
+ trace_mark(rcupreempt_trace_try_flip_e1, "NULL");
return;
}

@@ -778,7 +754,7 @@ void rcu_check_callbacks_rt(int cpu, int
if (rcu_ctrlblk.completed == rdp->completed)
rcu_try_flip();
spin_lock_irqsave(&rdp->lock, oldirq);
- RCU_TRACE_RDP(rcupreempt_trace_check_callbacks, rdp);
+ trace_mark(rcupreempt_trace_check_callbacks, "NULL");
__rcu_advance_callbacks(rdp);
spin_unlock_irqrestore(&rdp->lock, oldirq);
}
@@ -798,7 +774,7 @@ void rcu_advance_callbacks_rt(int cpu, i
return;
}
spin_lock_irqsave(&rdp->lock, oldirq);
- RCU_TRACE_RDP(rcupreempt_trace_check_callbacks, rdp);
+ trace_mark(rcupreempt_trace_check_callbacks, "NULL");
__rcu_advance_callbacks(rdp);
spin_unlock_irqrestore(&rdp->lock, oldirq);
}
@@ -900,13 +876,13 @@ void rcu_process_callbacks_rt(struct sof
}
rdp->donelist = NULL;
rdp->donetail = &rdp->donelist;
- RCU_TRACE_RDP(rcupreempt_trace_done_remove, rdp);
+ trace_mark(rcupreempt_trace_done_remove, "NULL");
spin_unlock_irqrestore(&rdp->lock, flags);
while (list) {
next = list->next;
list->func(list);
list = next;
- RCU_TRACE_ME(rcupreempt_trace_invoke);
+ trace_mark(rcupreempt_trace_invoke, "NULL");
}
}

@@ -924,7 +900,7 @@ void fastcall call_rcu_preempt(struct rc
__rcu_advance_callbacks(rdp);
*rdp->nexttail = head;
rdp->nexttail = &head->next;
- RCU_TRACE_RDP(rcupreempt_trace_next_add, rdp);
+ trace_mark(rcupreempt_trace_next_add, "NULL");
spin_unlock(&rdp->lock);
local_irq_restore(oldirq);
}
@@ -1007,7 +983,6 @@ void synchronize_kernel(void)
synchronize_rcu();
}

-#ifdef CONFIG_RCU_TRACE
int *rcupreempt_flipctr(int cpu)
{
return &per_cpu(rcu_flipctr, cpu)[0];
@@ -1031,13 +1006,3 @@ char *rcupreempt_try_flip_state_name(voi
return rcu_try_flip_state_names[rcu_try_flip_state];
}
EXPORT_SYMBOL_GPL(rcupreempt_try_flip_state_name);
-
-struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu)
-{
- struct rcu_data *rdp = RCU_DATA_CPU(cpu);
-
- return &rdp->trace;
-}
-EXPORT_SYMBOL_GPL(rcupreempt_trace_cpu);
-
-#endif /* #ifdef RCU_TRACE */
Index: linux-2.6.24-rc5-rt1.RCU_MARKERS/kernel/rcupreempt_trace.c
===================================================================
--- linux-2.6.24-rc5-rt1.RCU_MARKERS.orig/kernel/rcupreempt_trace.c
+++ linux-2.6.24-rc5-rt1.RCU_MARKERS/kernel/rcupreempt_trace.c
@@ -43,11 +43,19 @@
#include <linux/mutex.h>
#include <linux/rcupreempt_trace.h>
#include <linux/debugfs.h>
+#include <linux/percpu.h>

static struct mutex rcupreempt_trace_mutex;
static char *rcupreempt_trace_buf;
#define RCUPREEMPT_TRACE_BUF_SIZE 4096

+static DEFINE_PER_CPU(struct rcupreempt_trace, trace_data);
+
+struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu)
+{
+ return &per_cpu(trace_data, cpu);
+}
+
void rcupreempt_trace_move2done(struct rcupreempt_trace *trace)
{
trace->done_length += trace->wait_length;
@@ -135,6 +143,51 @@ void rcupreempt_trace_next_add(struct rc
trace->next_length++;
}

+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_move2done);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_move2wait);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_1);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_e1);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_i1);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_ie1);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_g1);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_a1);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_ae1);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_a2);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_z1);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_ze1);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_z2);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_m1);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_me1);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_try_flip_m2);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_check_callbacks);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_done_remove);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_invoke);
+DEFINE_RCUPREEMPT_MARKER_HANDLER(rcupreempt_trace_next_add);
+
+static struct rcupreempt_probe_data rcupreempt_probe_array[] =
+{
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_move2done),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_move2wait),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_1),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_e1),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_i1),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_ie1),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_g1),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_a1),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_ae1),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_a2),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_z1),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_ze1),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_z2),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_m1),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_me1),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_try_flip_m2),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_check_callbacks),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_done_remove),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_invoke),
+ INIT_RCUPREEMPT_PROBE(rcupreempt_trace_next_add)
+};
+
static void rcupreempt_trace_sum(struct rcupreempt_trace *sp)
{
struct rcupreempt_trace *cp;
@@ -297,9 +350,6 @@ static int rcupreempt_debugfs_init(void)
if (!ctrsdir)
goto free_out;

- if (!rcu_trace_boost_create(rcudir))
- goto free_out;
-
return 0;
free_out:
if (ctrsdir)
@@ -316,6 +366,21 @@ out:
static int __init rcupreempt_trace_init(void)
{
int ret;
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(rcupreempt_probe_array); i++) {
+ struct rcupreempt_probe_data *p = &rcupreempt_probe_array[i];
+ ret = marker_probe_register(p->name, p->format,
+ p->probe_func, p);
+ if (ret)
+ printk(KERN_INFO "Unable to register rcupreempt \
+ probe %s\n", rcupreempt_probe_array[i].name);
+ ret = marker_arm(p->name);
+ if (ret)
+ printk(KERN_INFO "Unable to arm rcupreempt probe %s\n",
+ p->name);
+ }
+ printk(KERN_INFO "RCU Preempt markers registered\n");

mutex_init(&rcupreempt_trace_mutex);
rcupreempt_trace_buf = kmalloc(RCUPREEMPT_TRACE_BUF_SIZE, GFP_KERNEL);
@@ -329,7 +394,12 @@ static int __init rcupreempt_trace_init(

static void __exit rcupreempt_trace_cleanup(void)
{
- rcu_trace_boost_destroy();
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(rcupreempt_probe_array); i++)
+ marker_probe_unregister(rcupreempt_probe_array[i].name);
+ printk(KERN_INFO "RCU Preempt markers unregistered\n");
+
debugfs_remove(statdir);
debugfs_remove(gpdir);
debugfs_remove(ctrsdir);
@@ -337,6 +407,7 @@ static void __exit rcupreempt_trace_clea
kfree(rcupreempt_trace_buf);
}

+MODULE_LICENSE("GPL");

module_init(rcupreempt_trace_init);
module_exit(rcupreempt_trace_cleanup);
Index: linux-2.6.24-rc5-rt1.RCU_MARKERS/kernel/Kconfig.preempt
===================================================================
--- linux-2.6.24-rc5-rt1.RCU_MARKERS.orig/kernel/Kconfig.preempt
+++ linux-2.6.24-rc5-rt1.RCU_MARKERS/kernel/Kconfig.preempt
@@ -172,14 +172,15 @@ config PREEMPT_RCU_BOOST
possible OOM problems.

config RCU_TRACE
- bool "Enable tracing for RCU - currently stats in debugfs"
+ tristate "Enable tracing for RCU - currently stats in debugfs"
select DEBUG_FS
- default y
+ select MARKERS
+ default m
help
This option provides tracing in RCU which presents stats
in debugfs for debugging RCU implementation.

- Say Y here if you want to enable RCU tracing
+ Say Y/M here if you want to enable RCU tracing in-kernel/module.
Say N if you are unsure.

config SPINLOCK_BKL

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