svn commit: r347852 - in head/sys/compat/linuxkpi/common: include/linux src

[Johannes Lundberg]

Author: johalun
Date: Thu May 16 18:03:08 2019
New Revision: 347852
URL: https://svnweb.freebsd.org/changeset/base/347852

Log:
  LinuxKPI: Updates to tasklets for Linux 5.0.
  
  DRM drivers expect tasklets to have a counter for enable/disable calls.
  Also, add a few more tasklet locking functions.
  
  This patch is part of D19565
  
  Reviewed by:	hps
  Approved by:	imp (mentor), hps
  MFC after:	1 week

Modified:
  head/sys/compat/linuxkpi/common/include/linux/interrupt.h
  head/sys/compat/linuxkpi/common/src/linux_tasklet.c

Modified: head/sys/compat/linuxkpi/common/include/linux/interrupt.h
==============================================================================
--- head/sys/compat/linuxkpi/common/include/linux/interrupt.h	Thu May 16 18:02:09 2019	(r347851)
+++ head/sys/compat/linuxkpi/common/include/linux/interrupt.h	Thu May 16 18:03:08 2019	(r347852)
@@ -189,11 +189,14 @@ typedef void tasklet_func_t(unsigned long);
 struct tasklet_struct {
 	TAILQ_ENTRY(tasklet_struct) entry;
 	tasklet_func_t *func;
+	/* Our "state" implementation is different. Avoid same name as Linux. */
+	volatile u_int tasklet_state;
+	atomic_t count;
 	unsigned long data;
 };
 
 #define	DECLARE_TASKLET(name, func, data)	\
-struct tasklet_struct name = { { NULL, NULL }, func, data }
+struct tasklet_struct name = { { NULL, NULL }, func, ATOMIC_INIT(0), data }
 
 #define	tasklet_hi_schedule(t)	tasklet_schedule(t)
 
@@ -203,5 +206,8 @@ extern void tasklet_init(struct tasklet_struct *, task
     unsigned long data);
 extern void tasklet_enable(struct tasklet_struct *);
 extern void tasklet_disable(struct tasklet_struct *);
+extern int tasklet_trylock(struct tasklet_struct *);
+extern void tasklet_unlock(struct tasklet_struct *);
+extern void tasklet_unlock_wait(struct tasklet_struct *ts);
 
 #endif	/* _LINUX_INTERRUPT_H_ */

Modified: head/sys/compat/linuxkpi/common/src/linux_tasklet.c
==============================================================================
--- head/sys/compat/linuxkpi/common/src/linux_tasklet.c	Thu May 16 18:02:09 2019	(r347851)
+++ head/sys/compat/linuxkpi/common/src/linux_tasklet.c	Thu May 16 18:03:08 2019	(r347852)
@@ -41,20 +41,22 @@ __FBSDID("$FreeBSD$");
 #define	TASKLET_ST_BUSY 1
 #define	TASKLET_ST_EXEC 2
 #define	TASKLET_ST_LOOP 3
-#define	TASKLET_ST_PAUSED 4
 
 #define	TASKLET_ST_CMPSET(ts, old, new)	\
-	atomic_cmpset_ptr((volatile uintptr_t *)&(ts)->entry.tqe_prev, old, new)
+	atomic_cmpset_int((volatile u_int *)&(ts)->tasklet_state, old, new)
 
 #define	TASKLET_ST_SET(ts, new)	\
-	WRITE_ONCE(*(volatile uintptr_t *)&(ts)->entry.tqe_prev, new)
+	WRITE_ONCE(*(volatile u_int *)&(ts)->tasklet_state, new)
 
 #define	TASKLET_ST_GET(ts) \
-	READ_ONCE(*(volatile uintptr_t *)&(ts)->entry.tqe_prev)
+	READ_ONCE(*(volatile u_int *)&(ts)->tasklet_state)
 
+#define	TASKLET_ST_TESTANDSET(ts, new) \
+	atomic_testandset_int((volatile u_int *)&(ts)->tasklet_state, new)
+
 struct tasklet_worker {
 	struct mtx mtx;
-	TAILQ_HEAD(, tasklet_struct) head;
+	TAILQ_HEAD(tasklet_list, tasklet_struct) head;
 	struct grouptask gtask;
 } __aligned(CACHE_LINE_SIZE);
 
@@ -68,25 +70,34 @@ tasklet_handler(void *arg)
 {
 	struct tasklet_worker *tw = (struct tasklet_worker *)arg;
 	struct tasklet_struct *ts;
+	struct tasklet_struct *last;
 
 	linux_set_current(curthread);
 
 	TASKLET_WORKER_LOCK(tw);
+	last = TAILQ_LAST(&tw->head, tasklet_list);
 	while (1) {
 		ts = TAILQ_FIRST(&tw->head);
 		if (ts == NULL)
 			break;
 		TAILQ_REMOVE(&tw->head, ts, entry);
 
-		TASKLET_WORKER_UNLOCK(tw);
-		do {
-			/* reset executing state */
-			TASKLET_ST_SET(ts, TASKLET_ST_EXEC);
+		if (!atomic_read(&ts->count)) {
+			TASKLET_WORKER_UNLOCK(tw);
+			do {
+				/* reset executing state */
+				TASKLET_ST_SET(ts, TASKLET_ST_EXEC);
 
-			ts->func(ts->data);
+				ts->func(ts->data);
 
-		} while (TASKLET_ST_CMPSET(ts, TASKLET_ST_EXEC, TASKLET_ST_IDLE) == 0);
-		TASKLET_WORKER_LOCK(tw);
+			} while (TASKLET_ST_CMPSET(ts, TASKLET_ST_EXEC,
+			        TASKLET_ST_IDLE) == 0);
+			TASKLET_WORKER_LOCK(tw);
+		} else {
+			TAILQ_INSERT_TAIL(&tw->head, ts, entry);
+		}
+		if (ts == last)
+			break;
 	}
 	TASKLET_WORKER_UNLOCK(tw);
 }
@@ -140,6 +151,8 @@ tasklet_init(struct tasklet_struct *ts,
 	ts->entry.tqe_next = NULL;
 	ts->func = func;
 	ts->data = data;
+	atomic_set_int(&ts->tasklet_state, TASKLET_ST_IDLE);
+	atomic_set(&ts->count, 0);
 }
 
 void
@@ -158,6 +171,10 @@ void
 tasklet_schedule(struct tasklet_struct *ts)
 {
 
+	/* tasklet is paused */
+	if (atomic_read(&ts->count))
+		return;
+
 	if (TASKLET_ST_CMPSET(ts, TASKLET_ST_EXEC, TASKLET_ST_LOOP)) {
 		/* tasklet_handler() will loop */
 	} else if (TASKLET_ST_CMPSET(ts, TASKLET_ST_IDLE, TASKLET_ST_BUSY)) {
@@ -201,17 +218,39 @@ tasklet_kill(struct tasklet_struct *ts)
 void
 tasklet_enable(struct tasklet_struct *ts)
 {
-	(void) TASKLET_ST_CMPSET(ts, TASKLET_ST_PAUSED, TASKLET_ST_IDLE);
+
+	atomic_dec(&ts->count);
 }
 
 void
 tasklet_disable(struct tasklet_struct *ts)
 {
-	while (1) {
-		if (TASKLET_ST_GET(ts) == TASKLET_ST_PAUSED) 
-			break;
-		if (TASKLET_ST_CMPSET(ts, TASKLET_ST_IDLE, TASKLET_ST_PAUSED))
-			break;
+
+	atomic_inc(&ts->count);
+	tasklet_unlock_wait(ts);
+}
+
+int
+tasklet_trylock(struct tasklet_struct *ts)
+{
+
+	return (!TASKLET_ST_TESTANDSET(ts, TASKLET_ST_BUSY));
+}
+
+void
+tasklet_unlock(struct tasklet_struct *ts)
+{
+
+	TASKLET_ST_SET(ts, TASKLET_ST_IDLE);
+}
+
+void
+tasklet_unlock_wait(struct tasklet_struct *ts)
+{
+
+	WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "tasklet_kill() can sleep");
+
+	/* wait until tasklet is no longer busy */
+	while (TASKLET_ST_GET(ts) != TASKLET_ST_IDLE)
 		pause("W", 1);
-	}
 }