This is a note to let you know that I've just added the patch titled powerpc/kernel: Block interrupts when updating TIDR to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: powerpc-kernel-block-interrupts-when-updating-tidr.patch and it can be found in the queue-4.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 384dfd627f1ee67d028e6f14c6e9bf5a1e2a7a24 Mon Sep 17 00:00:00 2001 From: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx> Date: Tue, 28 Nov 2017 13:39:43 -0600 Subject: powerpc/kernel: Block interrupts when updating TIDR 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); } /* Patches currently in stable-queue which might be from sukadev@xxxxxxxxxxxxxxxxxx are queue-4.15/powerpc-kernel-block-interrupts-when-updating-tidr.patch queue-4.15/powerpc-vas-don-t-set-uses_vas-for-kernel-windows.patch