On Sat, 2014-05-03 at 18:42 +0200, Sebastian Andrzej Siewior wrote:
> 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 <bigeasy@xxxxxxxxxxxxx>
> ---
> Mike, I see that lockdep splat (sleeping while atomic) during cpu-hotplug.
> Don't you see this, too?
Nope, didn't.
> block/blk-mq-cpu.c | 17 ++++++++++-------
> block/blk-mq.c | 2 +-
> 2 files changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/block/blk-mq-cpu.c b/block/blk-mq-cpu.c
> index 136ef86..37acc3a 100644
> --- a/block/blk-mq-cpu.c
> +++ b/block/blk-mq-cpu.c
> @@ -11,7 +11,7 @@
> #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)
> @@ -19,12 +19,15 @@ static int blk_mq_main_cpu_notify(struct notifier_block *self,
> unsigned int cpu = (unsigned long) hcpu;
> struct blk_mq_cpu_notifier *notify;
>
> - raw_spin_lock(&blk_mq_cpu_notify_lock);
> + if (action != CPU_POST_DEAD && 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)
> notify->notify(notify->data, action, cpu);
>
> - raw_spin_unlock(&blk_mq_cpu_notify_lock);
> + spin_unlock(&blk_mq_cpu_notify_lock);
> return NOTIFY_OK;
> }
>
> @@ -32,16 +35,16 @@ void blk_mq_register_cpu_notifier(struct blk_mq_cpu_notifier *notifier)
> {
> 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,
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index da3af9f..d5e73d8 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -971,7 +971,7 @@ static void blk_mq_hctx_notify(void *data, unsigned long action,
> struct blk_mq_ctx *ctx;
> LIST_HEAD(tmp);
>
> - if (action != CPU_DEAD && action != CPU_DEAD_FROZEN)
> + if (action != CPU_POST_DEAD && action != CPU_POST_DEAD)
> return;
>
> /*
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