powerpc/kernel: Block interrupts when updating TIDR

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@vger.kernel.org # v4.15+
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 2fd01c9045ba784548b4a21a9a9471a52f919c47..69af583dce98d9daed0b7c05e93953cb72b51e4c 100644 (file)
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1515,14 +1515,15 @@ 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;
@@ -1530,9 +1531,9 @@ static int assign_thread_tidr(void)
                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;
        }
 
@@ -1541,9 +1542,11 @@ static int assign_thread_tidr(void)
 
 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);
 }
 
 /*