diff options
author | Cliff Wickman <cpw@sgi.com> | 2005-10-27 10:29:08 -0500 |
---|---|---|
committer | Tony Luck <tony.luck@intel.com> | 2005-10-27 16:15:03 -0700 |
commit | 4ac0068f44f192f2de95a7bb36df3e19767a45fb (patch) | |
tree | 7971afe201d63657fceeb5770eb8247711ce69aa /arch/ia64/kernel | |
parent | 72ab373a5688a78cbdaf3bf96012e597d5399bb7 (diff) |
[IA64] ptrace - find memory sharers on children list
In arch/ia64/kernel/ptrace.c there is a test for a peek or poke of a
register image (in register backing storage).
The test can be unnecessarily long (and occurs while holding the tasklist_lock).
Especially long on a large system with thousands of active tasks.
The ptrace caller (presumably a debugger) specifies the pid of
its target and an address to peek or poke. But the debugger could be
attached to several tasks.
The idea of find_thread_for_addr() is to find whether the target address
is in the RBS for any of those tasks.
Currently it searches the thread-list of the target pid. If that search
does not find a match, and the shared mm-struct's user count indicates
that there are other tasks sharing this address space (a rare occurrence),
a search is made of all the tasks in the system.
Another approach can drastically shorten this procedure.
It depends upon the fact that in order to peek or poke from/to any task,
the debugger must first attach to that task. And when it does, the
attached task is made a child of the debugger (is chained to its children list).
Therefore we can search just the debugger's children list.
Signed-off-by: Cliff Wickman <cpw@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Diffstat (limited to 'arch/ia64/kernel')
-rw-r--r-- | arch/ia64/kernel/ptrace.c | 26 |
1 files changed, 10 insertions, 16 deletions
diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c index bbb8bc7c055..9a9c1bd01db 100644 --- a/arch/ia64/kernel/ptrace.c +++ b/arch/ia64/kernel/ptrace.c @@ -589,6 +589,7 @@ find_thread_for_addr (struct task_struct *child, unsigned long addr) { struct task_struct *g, *p; struct mm_struct *mm; + struct list_head *this, *next; int mm_users; if (!(mm = get_task_mm(child))) @@ -600,28 +601,21 @@ find_thread_for_addr (struct task_struct *child, unsigned long addr) goto out; /* not multi-threaded */ /* - * First, traverse the child's thread-list. Good for scalability with - * NPTL-threads. + * Traverse the current process' children list. Every task that + * one attaches to becomes a child. And it is only attached children + * of the debugger that are of interest (ptrace_check_attach checks + * for this). */ - p = child; - do { - if (thread_matches(p, addr)) { - child = p; - goto out; - } - if (mm_users-- <= 1) - goto out; - } while ((p = next_thread(p)) != child); - - do_each_thread(g, p) { - if (child->mm != mm) + list_for_each_safe(this, next, ¤t->children) { + p = list_entry(this, struct task_struct, sibling); + if (p->mm != mm) continue; - if (thread_matches(p, addr)) { child = p; goto out; } - } while_each_thread(g, p); + } + out: mmput(mm); return child; |