From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Serge E. Hallyn" Subject: Re: debugging threaded apps running under a clone(CLONE_NEWPID) Date: Mon, 23 Feb 2009 12:21:53 -0600 Message-ID: <20090223182153.GD13151@us.ibm.com> References: <499EE0D1.1010001@fr.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <499EE0D1.1010001@fr.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: Cedric Le Goater Cc: Linux Containers , Linux Kernel Mailing List List-Id: containers.vger.kernel.org Quoting Cedric Le Goater (clg@fr.ibm.com): > Hello ! > > to debug threaded apps, gdb uses a special libthread_db which seeks in the > symbols of the exec the list of running threads. This list contains the glibc > 'struct pthread' descriptor with pids and tids which values are relative > to the namespace in which the threads were created. > > unless you run gdb in the same pid namespace, gdb will not see any thread > in the debugged app. this is frustrating for some scenarios and some > support from the kernel would be needed to address this issue. Here > are some ideas : > > . enter a pid namespace. hard. > > . expose the pid numbers of a task in its pid namespaces, through some > ways like /proc/self/stat or /proc/self/pids and modify gdb to make > the conversion. > > How would you do it ? perhaps a /proc/$$/vpid which prints out task_pid_nr_ns(tsk, current->nsproxy->pidns) then each thread opens an fd for /proc/self/vpid and passes it over an af_unix socket to the parent gdb, which then reads it to get the pid in its own ns? -serge