On 09/01/2015 09:11 PM, Jorge Ramirez Ortiz wrote:
> On 09/01/2015 02:27 PM, Dmitriy Cherkasov wrote:
>> We have seen this before, but so far have not found a way to consistently
>> reproduce it.
>>
>> There are some caveats with the current way context switching is done in
>> Xenomai.
>>
>> On armv7, there was a completely separate implementation of
>> xnarch_switch_to(),
>> as well as separate fpu and TLS switching. At this stage for armv8 however,
>> we
>> are doing a direct call to the kernel's __switch_to(), which then performs
>> the
>> relevant register switches.
>>
>> Another possibility is that this may be lurking in the mm switch. During
>> calls
>> to check_and_switch_context(), the interrupt state may not always
>> match what is expected according to the comments in the original
>> version of that function.
>>
>> Overall, this mechanism could definitely benefit from further review.
>>
>
>
> Thanks Dimitry.
> I'll also try to look into this for this specific platform (however I am
> hopping
> that either Gilles or Philippe can spend some time on this soon)
>
> Just for completeness, as things stand this is pretty much that value I am
> seeing over consecutive runs.
>
> RTD| 4.167| 6.099| 11.667| 0| 0| 3.333|
> 66.667
> RTD| 4.167| 6.217| 13.333| 0| 0| 3.333|
> 66.667
> RTD| 4.167| 6.259| 11.667| 0| 0| 3.333|
> 66.667
> RTD| 4.167| 6.226| 12.500| 0| 0| 3.333|
> 66.667
> RTD| 4.167| 6.105| 11.667| 0| 0| 3.333|
> 66.667
> RTD| 4.167| 6.181| 12.500| 0| 0| 3.333|
> 66.667
> RTD| 4.167| 6.232| 12.500| 0| 0| 3.333|
> 66.667
> RTD| 4.167| 6.483| 20.000| 0| 0| 3.333|
> 66.667
> RTD| 4.167| 6.409| 9.167| 0| 0| 3.333|
> 66.667
> RTD| 4.167| 5.707| 12.500| 0| 0| 3.333|
> 66.667
> RTD| 4.167| 5.026| 6.667| 0| 0| 3.333|
> 66.667
> RTT| 00:15:04 (periodic user-mode task, 1000 us period, priority 99)
> RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat best|--lat
> worst
> RTD| 4.167| 5.025| 6.667| 0| 0| 3.333|
> 66.667
> Load script terminated, terminating checked scripts
> ---|-----------|-----------|-----------|--------|------|-------------------------
> RTS| 3.333| 6.540| 66.667| 0| 0| 00:15:04/00:15:04
> pipe_in: /tmp/xeno-test-in-9797
>
This won't address the current issue, but the notification of the head
domain on memory aborts needs fixing:
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index f363368..e59da5e 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -517,10 +517,10 @@ asmlinkage void __exception do_mem_abort(unsigned
long addr, unsigned int esr,
if (!inf->fn(addr, esr, regs))
return;
- irqflags = ipipe_fault_entry();
-
if (__ipipe_report_trap(IPIPE_TRAP_UNKNOWN, regs))
- goto out;
+ return;
+
+ irqflags = ipipe_fault_entry();
pr_alert("Unhandled fault: %s (0x%08x) at 0x%016lx\n",
inf->name, esr, addr);
@@ -530,7 +530,7 @@ asmlinkage void __exception do_mem_abort(unsigned
long addr, unsigned int esr,
info.si_code = inf->code;
info.si_addr = (void __user *)addr;
arm64_notify_die("", regs, &info, esr);
-out:
+
ipipe_fault_exit(irqflags);
}
@@ -544,17 +544,17 @@ asmlinkage void __exception
do_sp_pc_abort(unsigned long addr,
struct siginfo info;
unsigned long irqflags;
- irqflags = ipipe_fault_entry();
-
if (__ipipe_report_trap(IPIPE_TRAP_ALIGNMENT, regs))
- goto out;
+ return;
+
+ irqflags = ipipe_fault_entry();
info.si_signo = SIGBUS;
info.si_errno = 0;
info.si_code = BUS_ADRALN;
info.si_addr = (void __user *)addr;
arm64_notify_die("", regs, &info, esr);
-out:
+
ipipe_fault_exit(irqflags);
}
--
Philippe.
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