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

Allen
2024-03-28T17:52:28Z

On Wed, Mar 27, 2024 at 11:05 AM Corey Minyard <minyard@acm.org> wrote:
>
> 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.

My apologies, my scripts messed up the commit messages for this series.
Will have it fixed in v2.

>
> 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.

Fair point. Could you please let me know once you have had a chance to test
these changes. Meanwhile, I will work on RFC wherein IPMI will have its own
workqueue.

Thanks for taking time out to review.

- Allen

>
> -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
> >
> >
>

--
- Allen