Author: kib
Date: Fri Dec 30 20:21:53 2011
New Revision: 229021
URL: http://svn.freebsd.org/changeset/base/229021

Log:
  MFC r227393:
  Lock the thread lock around block that retrieves td_wmesg. Otherwise,
  procfs could see a thread with assigned td_wchan but still NULL td_wmesg.

Modified:
  stable/9/sys/fs/procfs/procfs_status.c
Directory Properties:
  stable/9/sys/   (props changed)

Modified: stable/9/sys/fs/procfs/procfs_status.c
==============================================================================
--- stable/9/sys/fs/procfs/procfs_status.c      Fri Dec 30 20:12:50 2011        
(r229020)
+++ stable/9/sys/fs/procfs/procfs_status.c      Fri Dec 30 20:21:53 2011        
(r229021)
@@ -113,12 +113,14 @@ procfs_doprocstatus(PFS_FILL_ARGS)
        }
 
        tdfirst = FIRST_THREAD_IN_PROC(p);
+       thread_lock(tdfirst);
        if (tdfirst->td_wchan != NULL) {
                KASSERT(tdfirst->td_wmesg != NULL,
                    ("wchan %p has no wmesg", tdfirst->td_wchan));
                wmesg = tdfirst->td_wmesg;
        } else
                wmesg = "nochan";
+       thread_unlock(tdfirst);
 
        if (p->p_flag & P_INMEM) {
                struct timeval start, ut, st;
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