Request for approval: 6929067: Stack guard pages should be removed when thread is detached

[Andreas Kohn]

On Fri, 2010-03-12 at 09:44 +0000, Andrew Haley wrote:
> On 03/11/2010 09:06 PM, Coleen Phillimore wrote:
> > 
> > I've added the test to the changeset and a script to run in our harness.
> > 
> > Also in os_linux.cpp, I changed the SYS_gettid call to go through our
> > os::Linux::gettid() because on at least one linux, syscall() returns a
> > long int which gets a compilation warning with %d.
> > 
> > open webrev at http://cr.openjdk.java.net/~coleenp/6929067/
> > bug link at http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6929067
> > 
> > Andrew, please have a look since you're the contributor.
> 
> That's OK, but you don't need SYS_gettid.
> Please look at http://cr.openjdk.java.net/~aph/6929067-jdk7-webrev-4/hotspot.patch
> I changed to "/proc/self/maps", as you requested.  I think this is better.
> 
> The copy of my webrev to cr.openjdk.java.net failed for some reason
> I don't understand.
> 

With this change I seem to hit the limit on the number of open files.
Looking through it, shouldn't get_stack_bounds() close the FILE* it
opened?

For example an eclipse process shows this:

/proc/20662/fd>ls -al |grep -c /proc/20662/maps
1917


+static bool
+get_stack_bounds(uintptr_t *bottom, uintptr_t *top)
+{
+  FILE *f = fopen("/proc/self/maps", "r");             <----- that one
+  if (f == NULL)
+    return false;
+
+  while (!feof(f)) {
+    size_t dummy;
+    char *str = NULL;
+    ssize_t len = getline(&str, &dummy, f);
+    if (len == -1) {
+      return false;
+    }
+
+    if (len > 0 && str[len-1] == '\n') {
+      str[len-1] = 0;
+      len--;
+    }
+
+    static const char *stack_str = "[stack]";
+    if (len > (ssize_t)strlen(stack_str)
+       && (strcmp(str + len - strlen(stack_str), stack_str) == 0)) {
+      if (sscanf(str, "%" SCNxPTR "-%" SCNxPTR, bottom, top) == 2) {
+        uintptr_t sp = (uintptr_t)__builtin_frame_address(0);
+        if (sp >= *bottom && sp <= *top) {
+          free(str);
+          return true;
+        }
+      }
+    }
+
+    free(str);
+  }
+
+  return false;
+}


Regards,
--
Andreas

-- 
Never attribute to malice that which can be adequately explained by
stupidity.                                        -- Hanlon's Razor
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