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

Greg Kroah-Hartman
2018-02-21T12:47:29Z

From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>

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

---
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);
}

/*