[tip:perfcounters/core] perf_counter: remove rq->lock usage

From: Peter Zijlstra
Date: Tue Apr 07 2009 - 05:12:40 EST

Commit-ID: 849691a6cd40270ff5f4a8846d5f6bf8df663ffc
Gitweb: http://git.kernel.org/tip/849691a6cd40270ff5f4a8846d5f6bf8df663ffc
Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
AuthorDate: Mon, 6 Apr 2009 11:45:12 +0200
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Tue, 7 Apr 2009 10:49:01 +0200

perf_counter: remove rq->lock usage

Now that all the task runtime clock users are gone, remove the ugly
rq->lock usage from perf counters, which solves the nasty deadlock
seen when a software task clock counter was read from an NMI overflow
context.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx>
LKML-Reference: <20090406094518.531137582@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>


---
include/linux/kernel_stat.h | 2 --
kernel/perf_counter.c | 42 ++++++++++++++++--------------------------
kernel/sched.c | 20 --------------------
3 files changed, 16 insertions(+), 48 deletions(-)

diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index b6d2887..080d1fd 100644
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -85,8 +85,6 @@ static inline unsigned int kstat_irqs(unsigned int irq)
/*
* Lock/unlock the current runqueue - to extract task statistics:
*/
-extern void curr_rq_lock_irq_save(unsigned long *flags);
-extern void curr_rq_unlock_irq_restore(unsigned long *flags);
extern unsigned long long __task_delta_exec(struct task_struct *tsk, int update);
extern unsigned long long task_delta_exec(struct task_struct *);

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 56b7eb5..f4f7596 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -172,8 +172,7 @@ static void __perf_counter_remove_from_context(void *info)
if (ctx->task && cpuctx->task_ctx != ctx)
return;

- curr_rq_lock_irq_save(&flags);
- spin_lock(&ctx->lock);
+ spin_lock_irqsave(&ctx->lock, flags);

counter_sched_out(counter, cpuctx, ctx);

@@ -198,8 +197,7 @@ static void __perf_counter_remove_from_context(void *info)
perf_max_counters - perf_reserved_percpu);
}

- spin_unlock(&ctx->lock);
- curr_rq_unlock_irq_restore(&flags);
+ spin_unlock_irqrestore(&ctx->lock, flags);
}


@@ -319,8 +317,7 @@ static void __perf_counter_disable(void *info)
if (ctx->task && cpuctx->task_ctx != ctx)
return;

- curr_rq_lock_irq_save(&flags);
- spin_lock(&ctx->lock);
+ spin_lock_irqsave(&ctx->lock, flags);

/*
* If the counter is on, turn it off.
@@ -336,8 +333,7 @@ static void __perf_counter_disable(void *info)
counter->state = PERF_COUNTER_STATE_OFF;
}

- spin_unlock(&ctx->lock);
- curr_rq_unlock_irq_restore(&flags);
+ spin_unlock_irqrestore(&ctx->lock, flags);
}

/*
@@ -515,8 +511,7 @@ static void __perf_install_in_context(void *info)
if (ctx->task && cpuctx->task_ctx != ctx)
return;

- curr_rq_lock_irq_save(&flags);
- spin_lock(&ctx->lock);
+ spin_lock_irqsave(&ctx->lock, flags);
update_context_time(ctx);

/*
@@ -565,8 +560,7 @@ static void __perf_install_in_context(void *info)
unlock:
hw_perf_restore(perf_flags);

- spin_unlock(&ctx->lock);
- curr_rq_unlock_irq_restore(&flags);
+ spin_unlock_irqrestore(&ctx->lock, flags);
}

/*
@@ -641,8 +635,7 @@ static void __perf_counter_enable(void *info)
if (ctx->task && cpuctx->task_ctx != ctx)
return;

- curr_rq_lock_irq_save(&flags);
- spin_lock(&ctx->lock);
+ spin_lock_irqsave(&ctx->lock, flags);
update_context_time(ctx);

counter->prev_state = counter->state;
@@ -678,8 +671,7 @@ static void __perf_counter_enable(void *info)
}

unlock:
- spin_unlock(&ctx->lock);
- curr_rq_unlock_irq_restore(&flags);
+ spin_unlock_irqrestore(&ctx->lock, flags);
}

/*
@@ -971,7 +963,7 @@ int perf_counter_task_disable(void)
if (likely(!ctx->nr_counters))
return 0;

- curr_rq_lock_irq_save(&flags);
+ local_irq_save(flags);
cpu = smp_processor_id();

perf_counter_task_sched_out(curr, cpu);
@@ -992,9 +984,7 @@ int perf_counter_task_disable(void)

hw_perf_restore(perf_flags);

- spin_unlock(&ctx->lock);
-
- curr_rq_unlock_irq_restore(&flags);
+ spin_unlock_irqrestore(&ctx->lock, flags);

return 0;
}
@@ -1011,7 +1001,7 @@ int perf_counter_task_enable(void)
if (likely(!ctx->nr_counters))
return 0;

- curr_rq_lock_irq_save(&flags);
+ local_irq_save(flags);
cpu = smp_processor_id();

perf_counter_task_sched_out(curr, cpu);
@@ -1037,7 +1027,7 @@ int perf_counter_task_enable(void)

perf_counter_task_sched_in(curr, cpu);

- curr_rq_unlock_irq_restore(&flags);
+ local_irq_restore(flags);

return 0;
}
@@ -1095,12 +1085,12 @@ static void __read(void *info)
struct perf_counter_context *ctx = counter->ctx;
unsigned long flags;

- curr_rq_lock_irq_save(&flags);
+ local_irq_save(flags);
if (ctx->is_active)
update_context_time(ctx);
counter->hw_ops->read(counter);
update_counter_times(counter);
- curr_rq_unlock_irq_restore(&flags);
+ local_irq_restore(flags);
}

static u64 perf_counter_read(struct perf_counter *counter)
@@ -2890,7 +2880,7 @@ __perf_counter_exit_task(struct task_struct *child,
* Be careful about zapping the list - IRQ/NMI context
* could still be processing it:
*/
- curr_rq_lock_irq_save(&flags);
+ local_irq_save(flags);
perf_flags = hw_perf_save_disable();

cpuctx = &__get_cpu_var(perf_cpu_context);
@@ -2903,7 +2893,7 @@ __perf_counter_exit_task(struct task_struct *child,
child_ctx->nr_counters--;

hw_perf_restore(perf_flags);
- curr_rq_unlock_irq_restore(&flags);
+ local_irq_restore(flags);
}

parent_counter = child_counter->parent;
diff --git a/kernel/sched.c b/kernel/sched.c
index f76e3c0..0de2f81 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -997,26 +997,6 @@ static struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags)
}
}

-void curr_rq_lock_irq_save(unsigned long *flags)
- __acquires(rq->lock)
-{
- struct rq *rq;
-
- local_irq_save(*flags);
- rq = cpu_rq(smp_processor_id());
- spin_lock(&rq->lock);
-}
-
-void curr_rq_unlock_irq_restore(unsigned long *flags)
- __releases(rq->lock)
-{
- struct rq *rq;
-
- rq = cpu_rq(smp_processor_id());
- spin_unlock(&rq->lock);
- local_irq_restore(*flags);
-}
-
void task_rq_unlock_wait(struct task_struct *p)
{
struct rq *rq = task_rq(p);
--
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