Re: [PATCH 6/9] ipmi: Convert from tasklet to BH workqueue

Corey Minyard
2024-03-27T17:58:27Z

On Wed, Mar 27, 2024 at 04:03:11PM +0000, Allen Pais wrote:
> The only generic interface to execute asynchronously in the BH context is
> tasklet; however, it's marked deprecated and has some design flaws. To
> replace tasklets, BH workqueue support was recently added. A BH workqueue
> behaves similarly to regular workqueues except that the queued work items
> are executed in the BH context.
>
> This patch converts drivers/infiniband/* from tasklet to BH workqueue.

I think you mean drivers/char/ipmi/* here.

I believe that work queues items are execute single-threaded for a work
queue, so this should be good. I need to test this, though. It may be
that an IPMI device can have its own work queue; it may not be important
to run it in bh context.

-corey

>
> Based on the work done by Tejun Heo <tj@kernel.org>
> Branch: https://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-6.10
>
> Signed-off-by: Allen Pais <allen.lkml@gmail.com>
> ---
> drivers/char/ipmi/ipmi_msghandler.c | 30 ++++++++++++++---------------
> 1 file changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
> index b0eedc4595b3..fce2a2dbdc82 100644
> --- a/drivers/char/ipmi/ipmi_msghandler.c
> +++ b/drivers/char/ipmi/ipmi_msghandler.c
> @@ -36,12 +36,13 @@
> #include <linux/nospec.h>
> #include <linux/vmalloc.h>
> #include <linux/delay.h>
> +#include <linux/workqueue.h>
>
> #define IPMI_DRIVER_VERSION "39.2"
>
> static struct ipmi_recv_msg *ipmi_alloc_recv_msg(void);
> static int ipmi_init_msghandler(void);
> -static void smi_recv_tasklet(struct tasklet_struct *t);
> +static void smi_recv_work(struct work_struct *t);
> static void handle_new_recv_msgs(struct ipmi_smi *intf);
> static void need_waiter(struct ipmi_smi *intf);
> static int handle_one_recv_msg(struct ipmi_smi *intf,
> @@ -498,13 +499,13 @@ struct ipmi_smi {
> /*
> * Messages queued for delivery. If delivery fails (out of memory
> * for instance), They will stay in here to be processed later in a
> - * periodic timer interrupt. The tasklet is for handling received
> + * periodic timer interrupt. The work is for handling received
> * messages directly from the handler.
> */
> spinlock_t waiting_rcv_msgs_lock;
> struct list_head waiting_rcv_msgs;
> atomic_t watchdog_pretimeouts_to_deliver;
> - struct tasklet_struct recv_tasklet;
> + struct work_struct recv_work;
>
> spinlock_t xmit_msgs_lock;
> struct list_head xmit_msgs;
> @@ -704,7 +705,7 @@ static void clean_up_interface_data(struct ipmi_smi *intf)
> struct cmd_rcvr *rcvr, *rcvr2;
> struct list_head list;
>
> - tasklet_kill(&intf->recv_tasklet);
> + cancel_work_sync(&intf->recv_work);
>
> free_smi_msg_list(&intf->waiting_rcv_msgs);
> free_recv_msg_list(&intf->waiting_events);
> @@ -1319,7 +1320,7 @@ static void free_user(struct kref *ref)
> {
> struct ipmi_user *user = container_of(ref, struct ipmi_user, refcount);
>
> - /* SRCU cleanup must happen in task context. */
> + /* SRCU cleanup must happen in work context. */
> queue_work(remove_work_wq, &user->remove_work);
> }
>
> @@ -3605,8 +3606,7 @@ int ipmi_add_smi(struct module *owner,
> intf->curr_seq = 0;
> spin_lock_init(&intf->waiting_rcv_msgs_lock);
> INIT_LIST_HEAD(&intf->waiting_rcv_msgs);
> - tasklet_setup(&intf->recv_tasklet,
> - smi_recv_tasklet);
> + INIT_WORK(&intf->recv_work, smi_recv_work);
> atomic_set(&intf->watchdog_pretimeouts_to_deliver, 0);
> spin_lock_init(&intf->xmit_msgs_lock);
> INIT_LIST_HEAD(&intf->xmit_msgs);
> @@ -4779,7 +4779,7 @@ static void handle_new_recv_msgs(struct ipmi_smi *intf)
> * To preserve message order, quit if we
> * can't handle a message. Add the message
> * back at the head, this is safe because this
> - * tasklet is the only thing that pulls the
> + * work is the only thing that pulls the
> * messages.
> */
> list_add(&smi_msg->link, &intf->waiting_rcv_msgs);
> @@ -4812,10 +4812,10 @@ static void handle_new_recv_msgs(struct ipmi_smi *intf)
> }
> }
>
> -static void smi_recv_tasklet(struct tasklet_struct *t)
> +static void smi_recv_work(struct work_struct *t)
> {
> unsigned long flags = 0; /* keep us warning-free. */
> - struct ipmi_smi *intf = from_tasklet(intf, t, recv_tasklet);
> + struct ipmi_smi *intf = from_work(intf, t, recv_work);
> int run_to_completion = intf->run_to_completion;
> struct ipmi_smi_msg *newmsg = NULL;
>
> @@ -4866,7 +4866,7 @@ void ipmi_smi_msg_received(struct ipmi_smi *intf,
>
> /*
> * To preserve message order, we keep a queue and deliver from
> - * a tasklet.
> + * a work.
> */
> if (!run_to_completion)
> spin_lock_irqsave(&intf->waiting_rcv_msgs_lock, flags);
> @@ -4887,9 +4887,9 @@ void ipmi_smi_msg_received(struct ipmi_smi *intf,
> spin_unlock_irqrestore(&intf->xmit_msgs_lock, flags);
>
> if (run_to_completion)
> - smi_recv_tasklet(&intf->recv_tasklet);
> + smi_recv_work(&intf->recv_work);
> else
> - tasklet_schedule(&intf->recv_tasklet);
> + queue_work(system_bh_wq, &intf->recv_work);
> }
> EXPORT_SYMBOL(ipmi_smi_msg_received);
>
> @@ -4899,7 +4899,7 @@ void ipmi_smi_watchdog_pretimeout(struct ipmi_smi *intf)
> return;
>
> atomic_set(&intf->watchdog_pretimeouts_to_deliver, 1);
> - tasklet_schedule(&intf->recv_tasklet);
> + queue_work(system_bh_wq, &intf->recv_work);
> }
> EXPORT_SYMBOL(ipmi_smi_watchdog_pretimeout);
>
> @@ -5068,7 +5068,7 @@ static bool ipmi_timeout_handler(struct ipmi_smi *intf,
> flags);
> }
>
> - tasklet_schedule(&intf->recv_tasklet);
> + queue_work(system_bh_wq, &intf->recv_work);
>
> return need_timer;
> }
> --
> 2.17.1
>
>