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rcu: Add tracing for _rcu_barrier()

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This commit adds event tracing for _rcu_barrier() execution.  This
is defined only if RCU_TRACE=y.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Paul E. McKenney
2012-05-23 18:47:05 -07:00
committed by Paul E. McKenney
parent cf3a9c4842
commit a83eff0a82
2 changed files with 73 additions and 1 deletions
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29
kernel/rcutree.c
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@@ -2259,6 +2259,17 @@ static int rcu_cpu_has_callbacks(int cpu)
rcu_preempt_cpu_has_callbacks(cpu);
}
/*
* Helper function for _rcu_barrier() tracing. If tracing is disabled,
* the compiler is expected to optimize this away.
*/
static void _rcu_barrier_trace(struct rcu_state *rsp, char *s,
int cpu, unsigned long done)
{
trace_rcu_barrier(rsp->name, s, cpu,
atomic_read(&rsp->barrier_cpu_count), done);
}
/*
* RCU callback function for _rcu_barrier(). If we are last, wake
* up the task executing _rcu_barrier().
@@ -2268,8 +2279,12 @@ static void rcu_barrier_callback(struct rcu_head *rhp)
struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head);
struct rcu_state *rsp = rdp->rsp;
if (atomic_dec_and_test(&rsp->barrier_cpu_count))
if (atomic_dec_and_test(&rsp->barrier_cpu_count)) {
_rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done);
complete(&rsp->barrier_completion);
} else {
_rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done);
}
}
/*
@@ -2280,6 +2295,7 @@ static void rcu_barrier_func(void *type)
struct rcu_state *rsp = type;
struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
_rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done);
atomic_inc(&rsp->barrier_cpu_count);
rsp->call(&rdp->barrier_head, rcu_barrier_callback);
}
@@ -2298,6 +2314,7 @@ static void _rcu_barrier(struct rcu_state *rsp)
unsigned long snap_done;
init_rcu_head_on_stack(&rd.barrier_head);
_rcu_barrier_trace(rsp, "Begin", -1, snap);
/* Take mutex to serialize concurrent rcu_barrier() requests. */
mutex_lock(&rsp->barrier_mutex);
@@ -2315,7 +2332,9 @@ static void _rcu_barrier(struct rcu_state *rsp)
* value up to the next even number and adds two before comparing.
*/
snap_done = ACCESS_ONCE(rsp->n_barrier_done);
_rcu_barrier_trace(rsp, "Check", -1, snap_done);
if (ULONG_CMP_GE(snap_done, ((snap + 1) & ~0x1) + 2)) {
_rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done);
smp_mb(); /* caller's subsequent code after above check. */
mutex_unlock(&rsp->barrier_mutex);
return;
@@ -2328,6 +2347,7 @@ static void _rcu_barrier(struct rcu_state *rsp)
*/
ACCESS_ONCE(rsp->n_barrier_done)++;
WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1);
_rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done);
smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */
/*
@@ -2364,13 +2384,19 @@ static void _rcu_barrier(struct rcu_state *rsp)
preempt_disable();
rdp = per_cpu_ptr(rsp->rda, cpu);
if (cpu_is_offline(cpu)) {
_rcu_barrier_trace(rsp, "Offline", cpu,
rsp->n_barrier_done);
preempt_enable();
while (cpu_is_offline(cpu) && ACCESS_ONCE(rdp->qlen))
schedule_timeout_interruptible(1);
} else if (ACCESS_ONCE(rdp->qlen)) {
_rcu_barrier_trace(rsp, "OnlineQ", cpu,
rsp->n_barrier_done);
smp_call_function_single(cpu, rcu_barrier_func, rsp, 1);
preempt_enable();
} else {
_rcu_barrier_trace(rsp, "OnlineNQ", cpu,
rsp->n_barrier_done);
preempt_enable();
}
}
@@ -2403,6 +2429,7 @@ static void _rcu_barrier(struct rcu_state *rsp)
smp_mb(); /* Keep increment after above mechanism. */
ACCESS_ONCE(rsp->n_barrier_done)++;
WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0);
_rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done);
smp_mb(); /* Keep increment before caller's subsequent code. */
/* Wait for all rcu_barrier_callback() callbacks to be invoked. */