Re: [Xenomai-core] Re: [PATCH] latency tracer update

[Philippe Gerum]

Jan Kiszka wrote:

Jan Kiszka wrote:

Jan Kiszka wrote:

...
Meanwhile I found a solution for the described unterminated trace (put
an explicite trace_end at the end of __ipipe_unstall_iret_root),
included the irq number in the begin/end report, and stumbled over some
other remaining unterminated trace on a different machine. So, no need
to hurry with the merge (not the review! ;) ), I will publish a second
revision first.

And here comes this revision finally. Should apply (almost) cleanly
against latest ipipe versions. Additionally to the changes of the first
revision this one addresses the following topics:

o fix trace overrun handling
o report IRQ number to tracer on IRQ entry/exit
o fix virtually leaking IRQs-off in __ipipe_unstall_iret_root()
o fix another potential NMI race
o really trace the maximum IRQs-off time, not the maximum time of
  consecutive IRQs-off times (that scenario will soon be addressed
  instead  in the latency benchmark tool => reset&freeze the maximum
  latency from the user's point of view)

...and it turned out that the existing functions were no sufficient for
this. So here comes an add-on patch to update3:

 o allow ipipe_trace_{frozen|max}_reset from every context
   (well, at least give it a try and just fail on locked traces)
 o mark border between valid and invalid trace points
 o show invalid points border

Apply order:

ipipe_tracer.update3
ipipe_tracer.update3-1

Merged in 1.1-03, with the appropriate tracer patch. Thanks.

The front-end to the first change, a modified latency+timerbench will
get committed to Xenomai soon. It already works nicely, automatically
creating a freeze of the maximum latency turn the benchmark perceives.

Jan


------------------------------------------------------------------------

--- linux-2.6.14.3/kernel/ipipe/tracer.c.orig   2006-01-06 11:13:41.000000000 
+0100
+++ linux-2.6.14.3/kernel/ipipe/tracer.c        2006-01-06 20:11:10.000000000 
+0100
@@ -134,10 +134,14 @@ __ipipe_migrate_pre_trace(struct ipipe_t
        int i;

new_tp->trace_pos = pre_trace+1;

+
        for (i = new_tp->trace_pos; i > 0; i--)
                memcpy(&new_tp->point[WRAP_POINT_NO(new_tp->trace_pos-i)],
                       &old_tp->point[WRAP_POINT_NO(old_pos-i)],
                       sizeof(struct ipipe_trace_point));
+
+       /* mark the end (i.e. the point before point[0]) invalid */
+       new_tp->point[IPIPE_TRACE_POINTS-1].eip = 0;
 }

static notrace struct ipipe_trace_path *

@@ -436,21 +440,23 @@ void notrace ipipe_trace_special(unsigne
 }
 EXPORT_SYMBOL(ipipe_trace_special);

-void ipipe_trace_max_reset(void)

+int ipipe_trace_max_reset(void)
 {
        int cpu_id;
        unsigned long flags;
        struct ipipe_trace_path *path;
+       int ret = 0;

- /* only allowed from root domain (we sync with /proc routines) */

-       if (ipipe_current_domain != ipipe_root_domain)
-               return;
-
-       down(&out_mutex);
        flags = __ipipe_global_path_lock();

for_each_cpu(cpu_id) {

                path = &trace_paths[cpu_id][max_path[cpu_id]];
+
+               if (path->dump_lock) {
+                       ret = -EBUSY;
+                       break;
+               }
+
                path->begin     = -1;
                path->end       = -1;
                path->trace_pos = 0;
@@ -458,25 +464,28 @@ void ipipe_trace_max_reset(void)
        }

__ipipe_global_path_unlock(flags);

-       up(&out_mutex);
+
+       return ret;
 }
 EXPORT_SYMBOL(ipipe_trace_max_reset);

-void ipipe_trace_frozen_reset(void)

+int ipipe_trace_frozen_reset(void)
 {
        int cpu_id;
        unsigned long flags;
        struct ipipe_trace_path *path;
+       int ret = 0;

- /* only allowed from root domain (we sync with /proc routines) */

-       if (ipipe_current_domain != ipipe_root_domain)
-               return;
-
-       down(&out_mutex);
        flags = __ipipe_global_path_lock();

for_each_cpu(cpu_id) {

                path = &trace_paths[cpu_id][frozen_path[cpu_id]];
+
+               if (path->dump_lock) {
+                       ret = -EBUSY;
+                       break;
+               }
+
                path->begin = -1;
                path->end = -1;
                path->trace_pos = 0;
@@ -484,7 +493,8 @@ void ipipe_trace_frozen_reset(void)
        }

__ipipe_global_path_unlock(flags);

-       up(&out_mutex);
+
+       return ret;
 }
 EXPORT_SYMBOL(ipipe_trace_frozen_reset);

@@ -684,8 +694,10 @@ static int __ipipe_prtrace_show(struct s

        unsigned long long abs_delta;
        struct ipipe_trace_point *point = p;

- if (!point->eip)

+       if (!point->eip) {
+               seq_puts(m, "-<invalid>-\n");
                return 0;
+       }

/* ipipe_tsc2us works on unsigned => handle sign separately */

        delta = point->timestamp -
@@ -749,7 +761,10 @@ static ssize_t
 __ipipe_max_reset(struct file *file, const char __user *pbuffer,
                   size_t count, loff_t *data)
 {
+       down(&out_mutex);
        ipipe_trace_max_reset();
+       up(&out_mutex);
+
        return count;
 }

@@ -841,7 +856,10 @@ static ssize_t

 __ipipe_frozen_reset(struct file *file, const char __user *pbuffer,
                      size_t count, loff_t *data)
 {
+       down(&out_mutex);
        ipipe_trace_frozen_reset();
+       up(&out_mutex);
+
        return count;
 }

--- linux-2.6.14.3/include/linux/ipipe_trace.h.orig 2006-01-06 11:13:41.000000000 +0100

+++ linux-2.6.14.3/include/linux/ipipe_trace.h  2006-01-06 12:37:19.000000000 
+0100
@@ -28,7 +28,7 @@ void ipipe_trace_end(unsigned long v);
 void ipipe_trace_freeze(unsigned long v);
 void ipipe_trace_special(unsigned char special_id, unsigned long v);

-void ipipe_trace_max_reset(void);

-void ipipe_trace_frozen_reset(void);
+int ipipe_trace_max_reset(void);
+int ipipe_trace_frozen_reset(void);

#endif /* !__LINUX_IPIPE_H */

--

Philippe.