LU-1735 ptlrpc: only set jobid if not already set

[fs/lustre-release.git] / libcfs / libcfs / linux / linux-curproc.c

diff --git a/libcfs/libcfs/linux/linux-curproc.c b/libcfs/libcfs/linux/linux-curproc.c
index f675eac..c1e814d 100644 (file)
--- a/libcfs/libcfs/linux/linux-curproc.c
+++ b/libcfs/libcfs/linux/linux-curproc.c
@@ -288,6 +288,14 @@ int cfs_get_environ(const char *key, char *value, int *val_len)
                RETURN(-EINVAL);
        }
 
+       /* Avoid deadlocks on mmap_sem if called from sys_mmap_pgoff(),
+        * which is already holding mmap_sem for writes.  If some other
+        * thread gets the write lock in the meantime, this thread will
+        * block, but at least it won't deadlock on itself.  LU-1735 */
+       if (down_read_trylock(&mm->mmap_sem) == 0)
+               return -EDEADLK;
+       up_read(&mm->mmap_sem);
+
        addr = mm->env_start;
        ret = -ENOENT;