From: Cliff Wickman Date: Thu, 27 Oct 2005 15:29:08 +0000 (-0500) Subject: [IA64] ptrace - find memory sharers on children list X-Git-Tag: v2.6.15-rc1~731^2~16^2^2~2^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4ac0068f44f192f2de95a7bb36df3e19767a45fb;p=pandora-kernel.git [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 Signed-off-by: Tony Luck --- Reading git-diff-tree failed