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perf_counter: Clean up task_ctx vs interrupts
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Remove the local_irq_save() etc.. in routines that are smp function
calls, or have IRQs disabled by other means.

Then change the COMM, MMAP, and swcounter context iteration to
current->perf_counter_ctxp and RCU, since it really doesn't matter
which context they iterate, they're all folded.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Peter Zijlstra authored and Ingo Molnar committed May 29, 2009
1 parent efb3d17 commit 665c214
Showing 1 changed file with 50 additions and 32 deletions.
82 changes: 50 additions & 32 deletions kernel/perf_counter.c
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Original file line number Diff line number Diff line change
Expand Up @@ -232,18 +232,14 @@ static void __perf_counter_remove_from_context(void *info)
struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_counter *counter = info;
struct perf_counter_context *ctx = counter->ctx;
unsigned long flags;

local_irq_save(flags);
/*
* If this is a task context, we need to check whether it is
* the current task context of this cpu. If not it has been
* scheduled out before the smp call arrived.
*/
if (ctx->task && cpuctx->task_ctx != ctx) {
local_irq_restore(flags);
if (ctx->task && cpuctx->task_ctx != ctx)
return;
}

spin_lock(&ctx->lock);
/*
Expand All @@ -267,7 +263,7 @@ static void __perf_counter_remove_from_context(void *info)
}

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


Expand Down Expand Up @@ -383,17 +379,13 @@ static void __perf_counter_disable(void *info)
struct perf_counter *counter = info;
struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_counter_context *ctx = counter->ctx;
unsigned long flags;

local_irq_save(flags);
/*
* If this is a per-task counter, need to check whether this
* counter's task is the current task on this cpu.
*/
if (ctx->task && cpuctx->task_ctx != ctx) {
local_irq_restore(flags);
if (ctx->task && cpuctx->task_ctx != ctx)
return;
}

spin_lock(&ctx->lock);

Expand All @@ -411,7 +403,7 @@ static void __perf_counter_disable(void *info)
counter->state = PERF_COUNTER_STATE_OFF;
}

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

/*
Expand Down Expand Up @@ -618,10 +610,8 @@ static void __perf_install_in_context(void *info)
struct perf_counter_context *ctx = counter->ctx;
struct perf_counter *leader = counter->group_leader;
int cpu = smp_processor_id();
unsigned long flags;
int err;

local_irq_save(flags);
/*
* If this is a task context, we need to check whether it is
* the current task context of this cpu. If not it has been
Expand All @@ -630,10 +620,8 @@ static void __perf_install_in_context(void *info)
* on this cpu because it had no counters.
*/
if (ctx->task && cpuctx->task_ctx != ctx) {
if (cpuctx->task_ctx || ctx->task != current) {
local_irq_restore(flags);
if (cpuctx->task_ctx || ctx->task != current)
return;
}
cpuctx->task_ctx = ctx;
}

Expand Down Expand Up @@ -687,7 +675,7 @@ static void __perf_install_in_context(void *info)
unlock:
perf_enable();

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

/*
Expand Down Expand Up @@ -751,19 +739,15 @@ static void __perf_counter_enable(void *info)
struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_counter_context *ctx = counter->ctx;
struct perf_counter *leader = counter->group_leader;
unsigned long flags;
int err;

local_irq_save(flags);
/*
* If this is a per-task counter, need to check whether this
* counter's task is the current task on this cpu.
*/
if (ctx->task && cpuctx->task_ctx != ctx) {
if (cpuctx->task_ctx || ctx->task != current) {
local_irq_restore(flags);
if (cpuctx->task_ctx || ctx->task != current)
return;
}
cpuctx->task_ctx = ctx;
}

Expand Down Expand Up @@ -811,7 +795,7 @@ static void __perf_counter_enable(void *info)
}

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

/*
Expand Down Expand Up @@ -981,6 +965,10 @@ void perf_counter_task_sched_out(struct task_struct *task,
spin_lock(&ctx->lock);
spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
if (context_equiv(ctx, next_ctx)) {
/*
* XXX do we need a memory barrier of sorts
* wrt to rcu_dereference() of perf_counter_ctxp
*/
task->perf_counter_ctxp = next_ctx;
next->perf_counter_ctxp = ctx;
ctx->task = next;
Expand All @@ -998,6 +986,9 @@ void perf_counter_task_sched_out(struct task_struct *task,
}
}

/*
* Called with IRQs disabled
*/
static void __perf_counter_task_sched_out(struct perf_counter_context *ctx)
{
struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
Expand All @@ -1012,6 +1003,9 @@ static void __perf_counter_task_sched_out(struct perf_counter_context *ctx)
cpuctx->task_ctx = NULL;
}

/*
* Called with IRQs disabled
*/
static void perf_counter_cpu_sched_out(struct perf_cpu_context *cpuctx)
{
__perf_counter_sched_out(&cpuctx->ctx, cpuctx);
Expand Down Expand Up @@ -2431,6 +2425,7 @@ static void perf_counter_comm_ctx(struct perf_counter_context *ctx,
static void perf_counter_comm_event(struct perf_comm_event *comm_event)
{
struct perf_cpu_context *cpuctx;
struct perf_counter_context *ctx;
unsigned int size;
char *comm = comm_event->task->comm;

Expand All @@ -2443,9 +2438,17 @@ static void perf_counter_comm_event(struct perf_comm_event *comm_event)

cpuctx = &get_cpu_var(perf_cpu_context);
perf_counter_comm_ctx(&cpuctx->ctx, comm_event);
if (cpuctx->task_ctx)
perf_counter_comm_ctx(cpuctx->task_ctx, comm_event);
put_cpu_var(perf_cpu_context);

rcu_read_lock();
/*
* doesn't really matter which of the child contexts the
* events ends up in.
*/
ctx = rcu_dereference(current->perf_counter_ctxp);
if (ctx)
perf_counter_comm_ctx(ctx, comm_event);
rcu_read_unlock();
}

void perf_counter_comm(struct task_struct *task)
Expand Down Expand Up @@ -2536,6 +2539,7 @@ static void perf_counter_mmap_ctx(struct perf_counter_context *ctx,
static void perf_counter_mmap_event(struct perf_mmap_event *mmap_event)
{
struct perf_cpu_context *cpuctx;
struct perf_counter_context *ctx;
struct file *file = mmap_event->file;
unsigned int size;
char tmp[16];
Expand Down Expand Up @@ -2568,10 +2572,18 @@ static void perf_counter_mmap_event(struct perf_mmap_event *mmap_event)

cpuctx = &get_cpu_var(perf_cpu_context);
perf_counter_mmap_ctx(&cpuctx->ctx, mmap_event);
if (cpuctx->task_ctx)
perf_counter_mmap_ctx(cpuctx->task_ctx, mmap_event);
put_cpu_var(perf_cpu_context);

rcu_read_lock();
/*
* doesn't really matter which of the child contexts the
* events ends up in.
*/
ctx = rcu_dereference(current->perf_counter_ctxp);
if (ctx)
perf_counter_mmap_ctx(ctx, mmap_event);
rcu_read_unlock();

kfree(buf);
}

Expand Down Expand Up @@ -2882,6 +2894,7 @@ static void __perf_swcounter_event(enum perf_event_types type, u32 event,
{
struct perf_cpu_context *cpuctx = &get_cpu_var(perf_cpu_context);
int *recursion = perf_swcounter_recursion_context(cpuctx);
struct perf_counter_context *ctx;

if (*recursion)
goto out;
Expand All @@ -2891,10 +2904,15 @@ static void __perf_swcounter_event(enum perf_event_types type, u32 event,

perf_swcounter_ctx_event(&cpuctx->ctx, type, event,
nr, nmi, regs, addr);
if (cpuctx->task_ctx) {
perf_swcounter_ctx_event(cpuctx->task_ctx, type, event,
nr, nmi, regs, addr);
}
rcu_read_lock();
/*
* doesn't really matter which of the child contexts the
* events ends up in.
*/
ctx = rcu_dereference(current->perf_counter_ctxp);
if (ctx)
perf_swcounter_ctx_event(ctx, type, event, nr, nmi, regs, addr);
rcu_read_unlock();

barrier();
(*recursion)--;
Expand Down

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