* [PATCH] Use raw_smp_processor_id() in rcu_random()
@ 2007-10-12 9:20 Gautham R Shenoy
2007-10-12 9:39 ` Josh Triplett
2007-10-12 19:21 ` Paul E. McKenney
0 siblings, 2 replies; 3+ messages in thread
From: Gautham R Shenoy @ 2007-10-12 9:20 UTC (permalink / raw)
To: Paul E McKenney, josh
Cc: linux-kernel, Andrew Morton, Oleg Nesterov, Dipankar Sarma,
rostedt
With CONFIG_PREEMPT=y on 2.6.23-rc8-mm2, rcu_random() calls
smp_processor_id() from a preemptible context, triggering the
following kernel error.
BUG: using smp_processor_id() in preemptible [00000001] code: rcu_torture_fak/5155
caller is rcu_random+0x16/0x39 [rcutorture]
[<c010612f>] dump_trace+0x68/0x1d2
[<c01062b1>] show_trace_log_lvl+0x18/0x2c
[<c0106c23>] show_trace+0xf/0x11
[<c0106d33>] dump_stack+0x12/0x14
[<c02a0a25>] debug_smp_processor_id+0xa1/0xb4
[<f887064c>] rcu_random+0x16/0x39 [rcutorture]
[<f8870cdf>] <3>BUG: using smp_processor_id() in preemptible [00000001] code: rcu_torture_fak/5156
rcu_torture_fakewriter+0x4d/0xc5 [rcutorture]
[<c0139b32>] caller is rcu_random+0x16/0x39 [rcutorture]
kthread+0x38/0x5e
[<c0105ca7>] kernel_thread_helper+0x7/0x10
=======================
[<c010612f>] dump_trace+0x68/0x1d2
[<c01062b1>] show_trace_log_lvl+0x18/0x2c
[<c0106c23>] show_trace+0xf/0x11
[<c0106d33>] dump_stack+0x12/0x14
[<c02a0a25>] debug_smp_processor_id+0xa1/0xb4
[<f887064c>] rcu_random+0x16/0x39 [rcutorture]
[<f8870cdf>] rcu_torture_fakewriter+0x4d/0xc5 [rcutorture]
rcu_random() can do with raw_smp_processor_id() as a parameter to cpu_clock()
in this particular context.
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
---
kernel/rcutorture.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
Index: linux-2.6.23-rc8/kernel/rcutorture.c
===================================================================
--- linux-2.6.23-rc8.orig/kernel/rcutorture.c
+++ linux-2.6.23-rc8/kernel/rcutorture.c
@@ -170,7 +170,8 @@ static unsigned long
rcu_random(struct rcu_random_state *rrsp)
{
if (--rrsp->rrs_count < 0) {
- rrsp->rrs_state += (unsigned long)cpu_clock(smp_processor_id());
+ rrsp->rrs_state +=
+ (unsigned long)cpu_clock(raw_smp_processor_id());
rrsp->rrs_count = RCU_RANDOM_REFRESH;
}
rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
--
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] Use raw_smp_processor_id() in rcu_random()
2007-10-12 9:20 [PATCH] Use raw_smp_processor_id() in rcu_random() Gautham R Shenoy
@ 2007-10-12 9:39 ` Josh Triplett
2007-10-12 19:21 ` Paul E. McKenney
1 sibling, 0 replies; 3+ messages in thread
From: Josh Triplett @ 2007-10-12 9:39 UTC (permalink / raw)
To: ego
Cc: Paul E McKenney, linux-kernel, Andrew Morton, Oleg Nesterov,
Dipankar Sarma, rostedt
Gautham R Shenoy wrote:
> With CONFIG_PREEMPT=y on 2.6.23-rc8-mm2, rcu_random() calls
> smp_processor_id() from a preemptible context, triggering the
> following kernel error.
>
> BUG: using smp_processor_id() in preemptible [00000001] code: rcu_torture_fak/5155
> caller is rcu_random+0x16/0x39 [rcutorture]
> [<c010612f>] dump_trace+0x68/0x1d2
> [<c01062b1>] show_trace_log_lvl+0x18/0x2c
> [<c0106c23>] show_trace+0xf/0x11
> [<c0106d33>] dump_stack+0x12/0x14
> [<c02a0a25>] debug_smp_processor_id+0xa1/0xb4
> [<f887064c>] rcu_random+0x16/0x39 [rcutorture]
> [<f8870cdf>] <3>BUG: using smp_processor_id() in preemptible [00000001] code: rcu_torture_fak/5156
> rcu_torture_fakewriter+0x4d/0xc5 [rcutorture]
> [<c0139b32>] caller is rcu_random+0x16/0x39 [rcutorture]
> kthread+0x38/0x5e
> [<c0105ca7>] kernel_thread_helper+0x7/0x10
> =======================
> [<c010612f>] dump_trace+0x68/0x1d2
> [<c01062b1>] show_trace_log_lvl+0x18/0x2c
> [<c0106c23>] show_trace+0xf/0x11
> [<c0106d33>] dump_stack+0x12/0x14
> [<c02a0a25>] debug_smp_processor_id+0xa1/0xb4
> [<f887064c>] rcu_random+0x16/0x39 [rcutorture]
> [<f8870cdf>] rcu_torture_fakewriter+0x4d/0xc5 [rcutorture]
>
> rcu_random() can do with raw_smp_processor_id() as a parameter to cpu_clock()
> in this particular context.
>
> Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Looks reasonable to me.
Acked-by: Josh Triplett <josh@kernel.org>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] Use raw_smp_processor_id() in rcu_random()
2007-10-12 9:20 [PATCH] Use raw_smp_processor_id() in rcu_random() Gautham R Shenoy
2007-10-12 9:39 ` Josh Triplett
@ 2007-10-12 19:21 ` Paul E. McKenney
1 sibling, 0 replies; 3+ messages in thread
From: Paul E. McKenney @ 2007-10-12 19:21 UTC (permalink / raw)
To: Gautham R Shenoy
Cc: josh, linux-kernel, Andrew Morton, Oleg Nesterov, Dipankar Sarma,
rostedt
On Fri, Oct 12, 2007 at 02:50:44PM +0530, Gautham R Shenoy wrote:
>
> With CONFIG_PREEMPT=y on 2.6.23-rc8-mm2, rcu_random() calls
> smp_processor_id() from a preemptible context, triggering the
> following kernel error.
>
> BUG: using smp_processor_id() in preemptible [00000001] code: rcu_torture_fak/5155
> caller is rcu_random+0x16/0x39 [rcutorture]
> [<c010612f>] dump_trace+0x68/0x1d2
> [<c01062b1>] show_trace_log_lvl+0x18/0x2c
> [<c0106c23>] show_trace+0xf/0x11
> [<c0106d33>] dump_stack+0x12/0x14
> [<c02a0a25>] debug_smp_processor_id+0xa1/0xb4
> [<f887064c>] rcu_random+0x16/0x39 [rcutorture]
> [<f8870cdf>] <3>BUG: using smp_processor_id() in preemptible [00000001] code: rcu_torture_fak/5156
> rcu_torture_fakewriter+0x4d/0xc5 [rcutorture]
> [<c0139b32>] caller is rcu_random+0x16/0x39 [rcutorture]
> kthread+0x38/0x5e
> [<c0105ca7>] kernel_thread_helper+0x7/0x10
> =======================
> [<c010612f>] dump_trace+0x68/0x1d2
> [<c01062b1>] show_trace_log_lvl+0x18/0x2c
> [<c0106c23>] show_trace+0xf/0x11
> [<c0106d33>] dump_stack+0x12/0x14
> [<c02a0a25>] debug_smp_processor_id+0xa1/0xb4
> [<f887064c>] rcu_random+0x16/0x39 [rcutorture]
> [<f8870cdf>] rcu_torture_fakewriter+0x4d/0xc5 [rcutorture]
>
> rcu_random() can do with raw_smp_processor_id() as a parameter to cpu_clock()
> in this particular context.
Good catch!!!
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
>
> ---
> kernel/rcutorture.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> Index: linux-2.6.23-rc8/kernel/rcutorture.c
> ===================================================================
> --- linux-2.6.23-rc8.orig/kernel/rcutorture.c
> +++ linux-2.6.23-rc8/kernel/rcutorture.c
> @@ -170,7 +170,8 @@ static unsigned long
> rcu_random(struct rcu_random_state *rrsp)
> {
> if (--rrsp->rrs_count < 0) {
> - rrsp->rrs_state += (unsigned long)cpu_clock(smp_processor_id());
> + rrsp->rrs_state +=
> + (unsigned long)cpu_clock(raw_smp_processor_id());
> rrsp->rrs_count = RCU_RANDOM_REFRESH;
> }
> rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
> --
> Gautham R Shenoy
> Linux Technology Center
> IBM India.
> "Freedom comes with a price tag of responsibility, which is still a bargain,
> because Freedom is priceless!"
^ permalink raw reply [flat|nested] 3+ messages in thread
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2007-10-12 9:20 [PATCH] Use raw_smp_processor_id() in rcu_random() Gautham R Shenoy
2007-10-12 9:39 ` Josh Triplett
2007-10-12 19:21 ` Paul E. McKenney
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