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author | Oleg Nesterov <oleg@redhat.com> | 2010-08-10 18:03:07 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-08-11 08:59:19 -0700 |
commit | c7e49c1488ab20342eaaf38f1ca35a207f4c051d (patch) | |
tree | 43876a69cafbb49ce86f71ba5db88018ca7cc036 /lib | |
parent | 13d7e3a2dba6a79589ed34dc0b9114d7b5ff9eab (diff) | |
download | op-kernel-dev-c7e49c1488ab20342eaaf38f1ca35a207f4c051d.zip op-kernel-dev-c7e49c1488ab20342eaaf38f1ca35a207f4c051d.tar.gz |
ptrace: optimize exit_ptrace() for the likely case
exit_ptrace() takes tasklist_lock unconditionally. We need this lock to
avoid the race with ptrace_traceme(), it acts as a barrier.
Change its caller, forget_original_parent(), to call exit_ptrace() under
tasklist_lock. Change exit_ptrace() to drop and reacquire this lock if
needed.
This allows us to add the fastpath list_empty(ptraced) check. In the
likely no-tracees case exit_ptrace() just returns and we avoid the lock()
+ unlock() sequence.
"Zhang, Yanmin" <yanmin_zhang@linux.intel.com> suggested to add this
check, and he reports that this change adds about 11% improvement in some
tests.
Suggested-and-tested-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
0 files changed, 0 insertions, 0 deletions