Commit 5be8e070 authored Jul 23, 2013 by Hiroya Nozaki Committed by Greg Kroah-Hartman Jul 23, 2013

staging/lustre/ptlrpc: Race between start and stop service threads

When ptlrpc_start_thread fails to create a new thread, it will
finalize and free a struct ptlrpc_thread created and used here.
Considering this, it can be a problem when ptlrpc_svcpt_stop_thread
is driven and handles the struct ptlrpc_thread right after or right
before failure of cfs_create_thread. Because this situation let
the both of ptlrpc_start_thread and ptlrpc_svcpt_stop_threads
access the freed ptlrpc_thread and cause OS panic. Or, it may
happen that ptlrpc_svcpt_stop_threads waits forever holding an
already-freed waitq.

This patch adds an error handling into ptlrpc_start_thread to fix
this problem.

Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-2889
Lustre-change: http://review.whamcloud.com/5552


Signed-off-by: Hiroya Nozaki <nozaki.hiroya@jp.fujitsu.com>
Reviewed-by: Liang Zhen <liang.zhen@intel.com>
Reviewed-by: Nikitas Angelinas <nikitas_angelinas@xyratex.com>
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent a55e0f44

drivers/staging/lustre/lustre/ptlrpc/service.c

+12 −4

Original line number	Original line	Diff line number	Diff line
	@@ -2765,11 +2765,19 @@ int ptlrpc_start_thread(struct ptlrpc_service_part *svcpt, int wait)
	CERROR("cannot start thread '%s': rc %d\n",		CERROR("cannot start thread '%s': rc %d\n",
	thread->t_name, rc);		thread->t_name, rc);
	spin_lock(&svcpt->scp_lock);		spin_lock(&svcpt->scp_lock);
	list_del(&thread->t_link);
	--svcpt->scp_nthrs_starting;		--svcpt->scp_nthrs_starting;
			if (thread_is_stopping(thread)) {
			/* this ptlrpc_thread is being hanled
			* by ptlrpc_svcpt_stop_threads now
			*/
			thread_add_flags(thread, SVC_STOPPED);
			wake_up(&thread->t_ctl_waitq);
	spin_unlock(&svcpt->scp_lock);		spin_unlock(&svcpt->scp_lock);
			} else {
	OBD_FREE(thread, sizeof(*thread));		list_del(&thread->t_link);
			spin_unlock(&svcpt->scp_lock);
			OBD_FREE_PTR(thread);
			}
	RETURN(rc);		RETURN(rc);
	}		}