4.15-stable review patch. If anyone has any objections, please let me know.
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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); }
/*