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

From: Corey Minyard <[email-masked]>
Date: Thu, 28 Mar 2024 14:23:07 -0500

On Thu, Mar 28, 2024 at 10:52:16AM -0700, Allen wrote:
> On Wed, Mar 27, 2024 at 11:05 AM Corey Minyard <[email-masked]> wrote:
> >
> > 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.

After looking and thinking about it a bit, a BH context is still
probably the best for this.

I have tested this patch under load and various scenarios and it seems
to work ok.  So:

Tested-by: Corey Minyard <[email-masked]>
Acked-by: Corey Minyard <[email-masked]>

Or I can take this into my tree.

-corey

> 
> - Allen
> 
> >
> > -corey
> >
> > >
> > > Based on the work done by Tejun Heo <[email-masked]>
> > > Branch: https://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-610
> > >
> > > Signed-off-by: Allen Pais <[email-masked]>
> > > ---
> > >  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
>