[PATCH 4.15 020/163] powerpc/kernel: Block interrupts when updating TIDR

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>

commit 384dfd627f1ee67d028e6f14c6e9bf5a1e2a7a24 upstream.

clear_thread_tidr() is called in interrupt context as a part of delayed
put of the task structure (i.e as a part of timer interrupt). To prevent
a deadlock, block interrupts when holding vas_thread_id_lock to set/
clear TIDR for a task.

Fixes: ec233ede4c86 ("powerpc: Add support for setting SPRN_TIDR")
Cc: stable@xxxxxxxxxxxxxxx # v4.15+
Signed-off-by: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/powerpc/kernel/process.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1509,14 +1509,15 @@ static int assign_thread_tidr(void)
 {
 	int index;
 	int err;
+	unsigned long flags;
 
 again:
 	if (!ida_pre_get(&vas_thread_ida, GFP_KERNEL))
 		return -ENOMEM;
 
-	spin_lock(&vas_thread_id_lock);
+	spin_lock_irqsave(&vas_thread_id_lock, flags);
 	err = ida_get_new_above(&vas_thread_ida, 1, &index);
-	spin_unlock(&vas_thread_id_lock);
+	spin_unlock_irqrestore(&vas_thread_id_lock, flags);
 
 	if (err == -EAGAIN)
 		goto again;
@@ -1524,9 +1525,9 @@ again:
 		return err;
 
 	if (index > MAX_THREAD_CONTEXT) {
-		spin_lock(&vas_thread_id_lock);
+		spin_lock_irqsave(&vas_thread_id_lock, flags);
 		ida_remove(&vas_thread_ida, index);
-		spin_unlock(&vas_thread_id_lock);
+		spin_unlock_irqrestore(&vas_thread_id_lock, flags);
 		return -ENOMEM;
 	}
 
@@ -1535,9 +1536,11 @@ again:
 
 static void free_thread_tidr(int id)
 {
-	spin_lock(&vas_thread_id_lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&vas_thread_id_lock, flags);
 	ida_remove(&vas_thread_ida, id);
-	spin_unlock(&vas_thread_id_lock);
+	spin_unlock_irqrestore(&vas_thread_id_lock, flags);
 }
 
 /*