tree f1073546e7644d08b2879054893c5a2c097131eb
parent e56ba6090eb29a49fcb2cb36887fa421da7331a2
author Josh Gao <jmgao@google.com> 1468539792 -0700
committer gitbuildkicker <android-build@google.com> 1469146622 -0700

DO NOT MERGE: debuggerd: verify that traced threads belong to the right process.

Fix two races in debuggerd's PTRACE_ATTACH logic:
  1. The target thread in a crash dump request could exit between the
     /proc/<pid>/task/<tid> check and the PTRACE_ATTACH.
  2. Sibling threads could exit between listing /proc/<pid>/task and the
     PTRACE_ATTACH.

Backport of NYC change I4dfe1ea30e2c211d2389321bd66e3684dd757591
Bug: http://b/29555636
Change-Id: I6c6efcf82a49bca140d761b2d1de04215ba4d252