Re: [PATCH] arch/arm64 :Cyclic Test fix in ARM64 fpsimd

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./cyclictest -p 80 -t5 -n  => Cyclic test is failing after 6Lack iterations
T: 0 ( 1364) P:99 I:1000 C: 668664 Min:      3 Act:    5 Avg:   11 Max:  100116

After analyzing the trace log , we observed the sudden change in
latency due to calling of fpsimd_preserve_current_state function.

Line 149766:     ntpd-925     1....1.. 512046976us :
fpsimd_preserve_current_state <-do_signal
Line 149768:     ntpd-925     1....1.. 512046977us : preempt_count_add
<-fpsimd_preserve_current_state
Line 149770:     ntpd-925     1....2.. 512046978us : preempt_count_sub
<-fpsimd_preserve_current_state

.......
Line 163170: cyclicte-964     0.....11 512065181us :
tracing_mark_write: hit latency threshold (98383 > 500)


Thanks and regards,
Ayyappa.Ch

...

On Thu, May 7, 2015 at 1:08 AM, Anders Roxell <anders.roxell@xxxxxxxxxx> wrote:
> On 2015-05-01 20:59, Ayyappa Ch wrote:
>> Floating point operations in arm64 should not disable preempt .
>
> I thought that I would see a problem if I ran a floating point
> workload and cyclictest at the same time but I don't.
>
> Can you please provide me some more details on how I can reproduce the
> problem?
>
> Cheers,
> Anders
>
>> Activating realtime features with below code.
>>
>> From e6a5fce9b3b55f48656240036a9354a0997c2907 Mon Sep 17 00:00:00 2001
>> From: Ayyappa Ch <ayyappa.chandolu@xxxxxxx>
>> Date: Tue, 28 Apr 2015 11:53:00 +0530
>> Subject: [PATCH ] floating point realtime fix
>>
>> ---
>>  arch/arm64/kernel/fpsimd.c | 16 ++++++++--------
>>  1 file changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
>> index 2438497..3dca156 100644
>> --- a/arch/arm64/kernel/fpsimd.c
>> +++ b/arch/arm64/kernel/fpsimd.c
>> @@ -166,10 +166,10 @@ void fpsimd_flush_thread(void)
>>   */
>>  void fpsimd_preserve_current_state(void)
>>  {
>> - preempt_disable();
>> + migrate_disable();
>>   if (!test_thread_flag(TIF_FOREIGN_FPSTATE))
>>   fpsimd_save_state(&current->thread.fpsimd_state);
>> - preempt_enable();
>> + migrate_enable();
>>  }
>>
>>  /*
>> @@ -179,7 +179,7 @@ void fpsimd_preserve_current_state(void)
>>   */
>>  void fpsimd_restore_current_state(void)
>>  {
>> - preempt_disable();
>> + migrate_disable();
>>   if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
>>   struct fpsimd_state *st = &current->thread.fpsimd_state;
>>
>> @@ -187,7 +187,7 @@ void fpsimd_restore_current_state(void)
>>   this_cpu_write(fpsimd_last_state, st);
>>   st->cpu = smp_processor_id();
>>   }
>> - preempt_enable();
>> + migrate_enable();
>>  }
>>
>>  /*
>> @@ -197,7 +197,7 @@ void fpsimd_restore_current_state(void)
>>   */
>>  void fpsimd_update_current_state(struct fpsimd_state *state)
>>  {
>> - preempt_disable();
>> + migrate_disable();
>>   fpsimd_load_state(state);
>>   if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
>>   struct fpsimd_state *st = &current->thread.fpsimd_state;
>> @@ -205,7 +205,7 @@ void fpsimd_update_current_state(struct fpsimd_state *state)
>>   this_cpu_write(fpsimd_last_state, st);
>>   st->cpu = smp_processor_id();
>>   }
>> - preempt_enable();
>> + migrate_enable();
>>  }
>>
>>  /*
>> @@ -239,7 +239,7 @@ void kernel_neon_begin_partial(u32 num_regs)
>>   * that there is no longer userland FPSIMD state in the
>>   * registers.
>>   */
>> - preempt_disable();
>> + migrate_disable();
>>   if (current->mm &&
>>      !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE))
>>   fpsimd_save_state(&current->thread.fpsimd_state);
>> @@ -255,7 +255,7 @@ void kernel_neon_end(void)
>>   in_irq() ? &hardirq_fpsimdstate : &softirq_fpsimdstate);
>>   fpsimd_load_partial_state(s);
>>   } else {
>> - preempt_enable();
>> + migrate_enable();
>>   }
>>  }
>>  EXPORT_SYMBOL(kernel_neon_end);
>>
>> On Fri, May 1, 2015 at 1:03 PM, Ayyappa Ch <ayyappa.ch.linux@xxxxxxxxx> wrote:
>> > Following Anders Roxell  patch on "Enable PREEMPT_RT_FULL" , observed
>> > one issue with Cyclic test while running floating point operations. So
>> > , modified below changes for that.
>> >
>> > From e6a5fce9b3b55f48656240036a9354a0997c2907 Mon Sep 17 00:00:00 2001
>> > From: Ayyappa Ch <ayyappa.chandolu@xxxxxxx>
>> > Date: Tue, 28 Apr 2015 11:53:00 +0530
>> > Subject: [PATCH ] floating point realtime fix
>> >
>> > ---
>> >  arch/arm64/kernel/fpsimd.c | 16 ++++++++--------
>> >  1 file changed, 8 insertions(+), 8 deletions(-)
>> >
>> > diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
>> > index 2438497..3dca156 100644
>> > --- a/arch/arm64/kernel/fpsimd.c
>> > +++ b/arch/arm64/kernel/fpsimd.c
>> > @@ -166,10 +166,10 @@ void fpsimd_flush_thread(void)
>> >   */
>> >  void fpsimd_preserve_current_state(void)
>> >  {
>> > - preempt_disable();
>> > + migrate_disable();
>> >   if (!test_thread_flag(TIF_FOREIGN_FPSTATE))
>> >   fpsimd_save_state(&current->thread.fpsimd_state);
>> > - preempt_enable();
>> > + migrate_enable();
>> >  }
>> >
>> >  /*
>> > @@ -179,7 +179,7 @@ void fpsimd_preserve_current_state(void)
>> >   */
>> >  void fpsimd_restore_current_state(void)
>> >  {
>> > - preempt_disable();
>> > + migrate_disable();
>> >   if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
>> >   struct fpsimd_state *st = &current->thread.fpsimd_state;
>> >
>> > @@ -187,7 +187,7 @@ void fpsimd_restore_current_state(void)
>> >   this_cpu_write(fpsimd_last_state, st);
>> >   st->cpu = smp_processor_id();
>> >   }
>> > - preempt_enable();
>> > + migrate_enable();
>> >  }
>> >
>> >  /*
>> > @@ -197,7 +197,7 @@ void fpsimd_restore_current_state(void)
>> >   */
>> >  void fpsimd_update_current_state(struct fpsimd_state *state)
>> >  {
>> > - preempt_disable();
>> > + migrate_disable();
>> >   fpsimd_load_state(state);
>> >   if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
>> >   struct fpsimd_state *st = &current->thread.fpsimd_state;
>> > @@ -205,7 +205,7 @@ void fpsimd_update_current_state(struct fpsimd_state *state)
>> >   this_cpu_write(fpsimd_last_state, st);
>> >   st->cpu = smp_processor_id();
>> >   }
>> > - preempt_enable();
>> > + migrate_enable();
>> >  }
>> >
>> >  /*
>> > @@ -239,7 +239,7 @@ void kernel_neon_begin_partial(u32 num_regs)
>> >   * that there is no longer userland FPSIMD state in the
>> >   * registers.
>> >   */
>> > - preempt_disable();
>> > + migrate_disable();
>> >   if (current->mm &&
>> >      !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE))
>> >   fpsimd_save_state(&current->thread.fpsimd_state);
>> > @@ -255,7 +255,7 @@ void kernel_neon_end(void)
>> >   in_irq() ? &hardirq_fpsimdstate : &softirq_fpsimdstate);
>> >   fpsimd_load_partial_state(s);
>> >   } else {
>> > - preempt_enable();
>> > + migrate_enable();
>> >   }
>> >  }
>> >  EXPORT_SYMBOL(kernel_neon_end);
>> > --
>> > 1.9.1
--
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