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Date: Tue, 25 May 2010 10:50:22 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: piotr@...owicz.com
Cc: linux-kernel@...r.kernel.org, Jens Axboe <jens.axboe@...cle.com>,
Divyesh Shah <dpshah@...gle.com>
Subject: Re: BUG: using smp_processor_id() in preemptible [00000000] code:
icedove-bin/5449
On Mon, 2010-05-24 at 05:03 +0200, Piotr Hosowicz wrote:
> [ 720.313607] BUG: using smp_processor_id() in preemptible [00000000] code: icedove-bin/5449
> [ 720.313612] caller is native_sched_clock+0x3c/0x68
> [ 720.313616] Pid: 5449, comm: icedove-bin Tainted: P 2.6.34-20100524-0407 #1
> [ 720.313618] Call Trace:
> [ 720.313624] [<ffffffff811a533b>] debug_smp_processor_id+0xc7/0xe0
> [ 720.313629] [<ffffffff81009b87>] native_sched_clock+0x3c/0x68
> [ 720.313634] [<ffffffff81009a4d>] sched_clock+0x9/0xd
> [ 720.313637] [<ffffffff811823ec>] blk_rq_init+0x92/0x9d
> [ 720.313641] [<ffffffff81184227>] get_request+0x1bf/0x2c7
> [ 720.313646] [<ffffffff8118435c>] get_request_wait+0x2d/0x19d
This comes from wreckage in the blk tree..
---
commit 9195291e5f05e01d67f9a09c756b8aca8f009089
Author: Divyesh Shah <dpshah@...gle.com>
Date: Thu Apr 1 15:01:41 2010 -0700
blkio: Increment the blkio cgroup stats for real now
We also add start_time_ns and io_start_time_ns fields to struct request
here to record the time when a request is created and when it is
dispatched to device. We use ns uints here as ms and jiffies are
not very useful for non-rotational media.
Signed-off-by: Divyesh Shah<dpshah@...gle.com>
Signed-off-by: Jens Axboe <jens.axboe@...cle.com>
---
+#ifdef CONFIG_BLK_CGROUP
+static inline void set_start_time_ns(struct request *req)
+{
+ req->start_time_ns = sched_clock();
+}
+
+static inline void set_io_start_time_ns(struct request *req)
+{
+ req->io_start_time_ns = sched_clock();
+}
+#else
+static inline void set_start_time_ns(struct request *req) {}
+static inline void set_io_start_time_ns(struct request *req) {}
+#endif
---
Clearly nobody tested this, and its terribly broken to boot.
I guess they want something like:
---
Subject: sched_clock: Add local_clock()
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Tue May 25 10:48:51 CEST 2010
For people who otherwise get to write: cpu_clock(smp_processor_id()),
there is now: local_clock().
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <new-submission>
---
Index: linux-2.6/arch/parisc/kernel/ftrace.c
===================================================================
--- linux-2.6.orig/arch/parisc/kernel/ftrace.c
+++ linux-2.6/arch/parisc/kernel/ftrace.c
@@ -82,7 +82,7 @@ unsigned long ftrace_return_to_handler(u
unsigned long ret;
pop_return_trace(&trace, &ret);
- trace.rettime = cpu_clock(raw_smp_processor_id());
+ trace.rettime = local_clock();
ftrace_graph_return(&trace);
if (unlikely(!ret)) {
@@ -126,7 +126,7 @@ void prepare_ftrace_return(unsigned long
return;
}
- calltime = cpu_clock(raw_smp_processor_id());
+ calltime = local_clock();
if (push_return_trace(old, calltime,
self_addr, &trace.depth) == -EBUSY) {
Index: linux-2.6/include/linux/blkdev.h
===================================================================
--- linux-2.6.orig/include/linux/blkdev.h
+++ linux-2.6/include/linux/blkdev.h
@@ -1213,12 +1213,12 @@ int kblockd_schedule_work(struct request
#ifdef CONFIG_BLK_CGROUP
static inline void set_start_time_ns(struct request *req)
{
- req->start_time_ns = sched_clock();
+ req->start_time_ns = local_clock();
}
static inline void set_io_start_time_ns(struct request *req)
{
- req->io_start_time_ns = sched_clock();
+ req->io_start_time_ns = local_clock();
}
static inline uint64_t rq_start_time_ns(struct request *req)
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -1822,6 +1822,7 @@ extern void sched_clock_idle_wakeup_even
* clock constructed from sched_clock():
*/
extern unsigned long long cpu_clock(int cpu);
+extern unsigned long long local_clock(void);
extern unsigned long long
task_sched_runtime(struct task_struct *task);
Index: linux-2.6/kernel/lockdep.c
===================================================================
--- linux-2.6.orig/kernel/lockdep.c
+++ linux-2.6/kernel/lockdep.c
@@ -146,7 +146,7 @@ static DEFINE_PER_CPU(struct lock_class_
static inline u64 lockstat_clock(void)
{
- return cpu_clock(smp_processor_id());
+ return local_clock();
}
static int lock_point(unsigned long points[], unsigned long ip)
Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -214,7 +214,7 @@ static void perf_unpin_context(struct pe
static inline u64 perf_clock(void)
{
- return cpu_clock(raw_smp_processor_id());
+ return local_clock();
}
/*
Index: linux-2.6/kernel/rcutorture.c
===================================================================
--- linux-2.6.orig/kernel/rcutorture.c
+++ linux-2.6/kernel/rcutorture.c
@@ -239,8 +239,7 @@ static unsigned long
rcu_random(struct rcu_random_state *rrsp)
{
if (--rrsp->rrs_count < 0) {
- rrsp->rrs_state +=
- (unsigned long)cpu_clock(raw_smp_processor_id());
+ rrsp->rrs_state += (unsigned long)local_clock();
rrsp->rrs_count = RCU_RANDOM_REFRESH;
}
rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -1670,7 +1670,7 @@ static void update_shares(struct sched_d
if (root_task_group_empty())
return;
- now = cpu_clock(raw_smp_processor_id());
+ now = local_clock();
elapsed = now - sd->last_update;
if (elapsed >= (s64)(u64)sysctl_sched_shares_ratelimit) {
Index: linux-2.6/kernel/sched_clock.c
===================================================================
--- linux-2.6.orig/kernel/sched_clock.c
+++ linux-2.6/kernel/sched_clock.c
@@ -249,6 +249,18 @@ unsigned long long cpu_clock(int cpu)
return clock;
}
+unsigned long long local_clock(void)
+{
+ unsigned long long clock;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ clock = sched_clock_cpu(smp_processor_id());
+ local_irq_restore(flags);
+
+ return clock;
+}
+
#else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */
void sched_clock_init(void)
@@ -264,12 +276,17 @@ u64 sched_clock_cpu(int cpu)
return sched_clock();
}
-
unsigned long long cpu_clock(int cpu)
{
return sched_clock_cpu(cpu);
}
+unsigned long long local_clock(void)
+{
+ return sched_clock_cpu(0);
+}
+
#endif /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */
EXPORT_SYMBOL_GPL(cpu_clock);
+EXPORT_SYMBOL_GPL(local_clock);
Index: linux-2.6/kernel/trace/trace_clock.c
===================================================================
--- linux-2.6.orig/kernel/trace/trace_clock.c
+++ linux-2.6/kernel/trace/trace_clock.c
@@ -56,7 +56,7 @@ u64 notrace trace_clock_local(void)
*/
u64 notrace trace_clock(void)
{
- return cpu_clock(raw_smp_processor_id());
+ return local_clock();
}
--
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