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

[Allen]

On Wed, Mar 27, 2024 at 11:05 AM Corey Minyard <minyard@xxxxxxx> 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@xxxxxxxxxx>
> > Branch: https://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-610
> >
> > Signed-off-by: Allen Pais <allen.lkml@xxxxxxxxx>
> > ---
> >  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