locking/mutex, drm: Introduce mutex_trylock_recursive()

By popular DRM demand, introduce mutex_trylock_recursive() to fix up the
two GEM users.

Without this it is very easy for these drivers to get stuck in
low-memory situations and trigger OOM. Work is in progress to remove the
need for this in at least i915.

Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: David Airlie <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Ding Tianhong <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: Jason Low <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rob Clark <[email protected]>
Cc: Terry Rudd <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tim Chen <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 6 insertions, 0 deletions

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index a8368d1c4348..23f462f64a3f 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6076,6 +6076,12 @@ sub process {
 			}
 		}
 
+# check for mutex_trylock_recursive usage
+		if ($line =~ /mutex_trylock_recursive/) {
+			ERROR("LOCKING",
+			      "recursive locking is bad, do not use this ever.\n" . $herecurr);
+		}
+
 # check for lockdep_set_novalidate_class
 		if ($line =~ /^.\s*lockdep_set_novalidate_class\s*\(/ ||
 		    $line =~ /__lockdep_no_validate__\s*\)/ ) {