Re: [PATCH] wp-replication: Fix test case loop

[Andreas Arnez <arnez at linux dot vnet dot ibm dot com>]

Luis Machado <lgustavo@codesourcery.com> writes:

> On 07/05/2013 01:10 PM, Andreas Arnez wrote:
>> When executing wp-replication.exp on S/390, the loop that counts the
>> number of available hardware watchpoints does not terminate properly,
>> because *all* "watch" commands yield "hardware watchpoints".
>>
>> Since the C source code is not prepared for more than NR_THREADS
>> hardware watchpoints anyhow, I suggest to add the appropriate exit
>> condition to the loop.
>
> That's an interesting behavior. Are the resources on s390 nearly
> unlimited for hardware watchpoints? Does it run out of hardware
> watchpoints eventually?

Well, that would be nice, wouldn't it?  But sorry, no.  On s390 the
hardware can generate so-called "PER storage alteration events" (PER =
program event recording) for a single contiguous memory area.
s390-nat.c chooses this area such that all desired watchpoints lie
within.

Thus what happens in wp-replication.exp is that the PER ending address
is increased with every loop iteration, but no hardware limit is
reached.

> If s390 doesn't run out of hardware watchpoints, i'd add a comment to
> the testcase explaining why we have this condition.

Sure.  How about this then?


diff --git a/gdb/testsuite/gdb.threads/wp-replication.exp b/gdb/testsuite/gdb.threads/wp-replication.exp
index 8927a43..c6a13b9 100644
--- a/gdb/testsuite/gdb.threads/wp-replication.exp
+++ b/gdb/testsuite/gdb.threads/wp-replication.exp
@@ -81,6 +81,14 @@ while { $done == 0 } {
   gdb_test_multiple "continue" "watchpoint created successfully" {
     -re ".*Breakpoint 2, empty_cycle \\(\\).*$gdb_prompt $" {
       incr hwatch_count
+
+      # Some targets (like S/390) behave as though supporting
+      # unlimited hardware watchpoints.  In this case we just take a
+      # safe exit out of the loop.
+      if { $hwatch_count == $NR_THREADS } {
+	set done 1
+	break
+      }
     }
     -re ".*Could not insert hardware watchpoint.*$gdb_prompt $" {
       set done 1