From: Sebastian Andrzej Siewior Date: Sat, 3 May 2014 11:00:29 +0200 Subject: blk-mq: revert raw locks, post pone notifier to POST_DEAD Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.4-rc6-rt1/patches-4.4-rc6-rt1.tar.xz The blk_mq_cpu_notify_lock should be raw because some CPU down levels are called with interrupts off. The notifier itself calls currently one function that is blk_mq_hctx_notify(). That function acquires the ctx->lock lock which is sleeping and I would prefer to keep it that way. That function only moves IO-requests from the CPU that is going offline to another CPU and it is currently the only one. Therefore I revert the list lock back to sleeping spinlocks and let the notifier run at POST_DEAD time. Signed-off-by: Sebastian Andrzej Siewior --- block/blk-mq-cpu.c | 17 ++++++++++------- block/blk-mq.c | 2 +- 2 files changed, 11 insertions(+), 8 deletions(-) --- a/block/blk-mq-cpu.c +++ b/block/blk-mq-cpu.c @@ -16,7 +16,7 @@ #include "blk-mq.h" static LIST_HEAD(blk_mq_cpu_notify_list); -static DEFINE_RAW_SPINLOCK(blk_mq_cpu_notify_lock); +static DEFINE_SPINLOCK(blk_mq_cpu_notify_lock); static int blk_mq_main_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) @@ -25,7 +25,10 @@ static int blk_mq_main_cpu_notify(struct struct blk_mq_cpu_notifier *notify; int ret = NOTIFY_OK; - raw_spin_lock(&blk_mq_cpu_notify_lock); + if (action != CPU_POST_DEAD) + return NOTIFY_OK; + + spin_lock(&blk_mq_cpu_notify_lock); list_for_each_entry(notify, &blk_mq_cpu_notify_list, list) { ret = notify->notify(notify->data, action, cpu); @@ -33,7 +36,7 @@ static int blk_mq_main_cpu_notify(struct break; } - raw_spin_unlock(&blk_mq_cpu_notify_lock); + spin_unlock(&blk_mq_cpu_notify_lock); return ret; } @@ -41,16 +44,16 @@ void blk_mq_register_cpu_notifier(struct { BUG_ON(!notifier->notify); - raw_spin_lock(&blk_mq_cpu_notify_lock); + spin_lock(&blk_mq_cpu_notify_lock); list_add_tail(¬ifier->list, &blk_mq_cpu_notify_list); - raw_spin_unlock(&blk_mq_cpu_notify_lock); + spin_unlock(&blk_mq_cpu_notify_lock); } void blk_mq_unregister_cpu_notifier(struct blk_mq_cpu_notifier *notifier) { - raw_spin_lock(&blk_mq_cpu_notify_lock); + spin_lock(&blk_mq_cpu_notify_lock); list_del(¬ifier->list); - raw_spin_unlock(&blk_mq_cpu_notify_lock); + spin_unlock(&blk_mq_cpu_notify_lock); } void blk_mq_init_cpu_notifier(struct blk_mq_cpu_notifier *notifier, --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1640,7 +1640,7 @@ static int blk_mq_hctx_notify(void *data { struct blk_mq_hw_ctx *hctx = data; - if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) + if (action == CPU_POST_DEAD) return blk_mq_hctx_cpu_offline(hctx, cpu); /*