From d73379a5a3b2d6381ccd578d843aae7ba36799cd Mon Sep 17 00:00:00 2001
From: Ben Gamari <ben@smart-cactus.org>
Date: Sun, 20 Oct 2019 15:51:08 -0400
Subject: Assert capability ownership

---
 rts/Capability.c | 4 ++++
 rts/Capability.h | 2 ++
 rts/ward.config  | 5 ++++-
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/rts/Capability.c b/rts/Capability.c
index 7d44b0ec38..194184b101 100644
--- a/rts/Capability.c
+++ b/rts/Capability.c
@@ -494,6 +494,7 @@ void interruptAllCapabilities(void)
 
 #if defined(THREADED_RTS)
 WARD_NEED(capability_lock_held)
+WARD_GRANT(TASK_OWNS_CAPABILITY(task, cap))
 static void
 giveCapabilityToTask (Capability *cap USED_IF_DEBUG, Task *task)
 {
@@ -777,6 +778,7 @@ static Capability * waitForWorkerCapability (Task *task)
 
 #if defined(THREADED_RTS)
 
+WARD_GRANT(TASK_OWNS_CAPABILITY(task, *return))
 static Capability * waitForReturnCapability (Task *task)
 {
     Capability *cap;
@@ -882,6 +884,7 @@ static Capability * find_capability_for_task(const Task * task)
  *
  * ------------------------------------------------------------------------- */
 
+WARD_GRANT(TASK_OWNS_CAPABILITY(task, *cap))
 void waitForCapability (Capability **pCap, Task *task)
 {
 #if !defined(THREADED_RTS)
@@ -956,6 +959,7 @@ void waitForCapability (Capability **pCap, Task *task)
 
 /* See Note [GC livelock] in Schedule.c for why we have gcAllowed
    and return the bool */
+WARD_REVOKE(TASK_OWNS_CAPABILITY(task, *cap))
 bool /* Did we GC? */
 yieldCapability
     ( Capability** pCap     // [in/out] Task's owned capability. Set to the
diff --git a/rts/Capability.h b/rts/Capability.h
index 78b7b6f083..ba19e3130d 100644
--- a/rts/Capability.h
+++ b/rts/Capability.h
@@ -386,6 +386,8 @@ void markCapabilities (evac_fn evac, void *user);
 
 void traverseSparkQueues (evac_fn evac, void *user);
 
+#define TASK_OWNS_CAPABILITY(task, cap) task_owns_capability
+
 WARD_GRANT(capability_lock_held)
 INLINE_HEADER void
 acquire_capability_lock(Capability *cap) {
diff --git a/rts/ward.config b/rts/ward.config
index cd34be6a1b..6585b1914e 100644
--- a/rts/ward.config
+++ b/rts/ward.config
@@ -14,7 +14,10 @@ gc_block_alloc_spin_held "gc_block_alloc_spin is held"
 
 stable_ptr_lock_held "the stable pointer lock is held";
 
-task_owns_capability "the current thread's Task owns the Capability";
+// N.B. Use the TASK_OWNS_CAPABILITY macro instead of this capability directly where
+// possible to clarify which Capability and which Task we are talking about.
+task_owns_capability "a Task owns the Capability";
+
 capability_lock_held "the Capability's lock is held";
 
 .enforce "Storage.c";
-- 
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