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Message-ID: <20080916123813.51ffd682@bull.net>
Date:	Tue, 16 Sep 2008 12:38:13 +0200
From:	Sebastien Dugue <sebastien.dugue@...l.net>
To:	Thomas Klein <osstklei@...ibm.com>
Cc:	tklein@...ibm.com, tinytim@...ibm.com, jeff@...zik.org,
	hering2@...ibm.com, netdev@...r.kernel.org, themann@...ibm.com,
	linux-kernel@...r.kernel.org, jean-pierre.dion@...l.net,
	linuxppc-dev@...abs.org, raisch@...ibm.com,
	gilles.carry@....bull.net
Subject: Re: [PATCH 2/2] ehea: fix mutex and spinlock use

On Tue, 16 Sep 2008 11:13:13 +0200 Thomas Klein <osstklei@...ibm.com> wrote:

> Sebastien Dugue wrote:
> > On Mon, 15 Sep 2008 17:18:27 +0200 Thomas Klein <osstklei@...ibm.com> wrote:
> > 
> >> NACK!
> >>
> >> I regret but this patch is wrong. It is not sufficient to only lock
> >> the replacement of an old list with a new list. Building up those
> >> lists is a 3-step process:
> >>
> >> 1. Count the number of entries a list will contain and allocate mem
> >> 2. Fill the list
> >> 3. Replace old list with updated list
> >>
> >> It's obvious that the contents of the list may not change during this
> >> procedure. That means that not only the list build-up procedure must
> >> be locked. It must be assured that no function that modifies the list's
> >> content can be called while another list update is in progress.
> >>
> >> Jeff, please revert this patch.
> > 
> >   OK, your call, you know the code better than I do.
> > 
> >   But the locking could at least be pushed into ehea_update_firmware_handles()
> > and ehea_update_bcmc_registrations() instead of being at each call site.
> > 
> >   Thanks,
> > 
> >   Sebastien.
> > 
> 
> It unfortunately can't. As I already mentioned "it must be assured that no
> function that modifies the list's content can be called while another list
> update is in progress". This means that for example ehea_broadcast_reg_helper()
> may not run during a list update. That's why the locks surround these function
> calls as well.

  OK, I see.

  Thanks,

  Sebastien.

> 
> Thomas
> 
> 
> >> Thanks
> >> Thomas
> >>
> >>
> >>
> >> Sebastien Dugue wrote:
> >>>   Looks like to me that the ehea_fw_handles.lock mutex and the
> >>> ehea_bcmc_regs.lock spinlock are taken much longer than necessary and could
> >>> as well be pushed inside the functions that need them
> >>> (ehea_update_firmware_handles() and ehea_update_bcmc_registrations())
> >>> rather than at each callsite.
> >>>
> >>> Signed-off-by: Sebastien Dugue <sebastien.dugue@...l.net>
> >>> ---
> >>>  drivers/net/ehea/ehea_main.c |   26 ++++----------------------
> >>>  1 files changed, 4 insertions(+), 22 deletions(-)
> >>>
> >>> diff --git a/drivers/net/ehea/ehea_main.c b/drivers/net/ehea/ehea_main.c
> >>> index b70c531..c765ec6 100644
> >>> --- a/drivers/net/ehea/ehea_main.c
> >>> +++ b/drivers/net/ehea/ehea_main.c
> >>> @@ -219,9 +219,11 @@ static void ehea_update_firmware_handles(void)
> >>>  	}
> >>>  
> >>>  out_update:
> >>> +	mutex_lock(&ehea_fw_handles.lock);
> >>>  	kfree(ehea_fw_handles.arr);
> >>>  	ehea_fw_handles.arr = arr;
> >>>  	ehea_fw_handles.num_entries = i;
> >>> +	mutex_unlock(&ehea_fw_handles.lock);
> >>>  }
> >>>  
> >>>  static void ehea_update_bcmc_registrations(void)
> >>> @@ -293,9 +295,11 @@ static void ehea_update_bcmc_registrations(void)
> >>>  	}
> >>>  
> >>>  out_update:
> >>> +	spin_lock(&ehea_bcmc_regs.lock);
> >>>  	kfree(ehea_bcmc_regs.arr);
> >>>  	ehea_bcmc_regs.arr = arr;
> >>>  	ehea_bcmc_regs.num_entries = i;
> >>> +	spin_unlock(&ehea_bcmc_regs.lock);
> >>>  }
> >>>  
> >>>  static struct net_device_stats *ehea_get_stats(struct net_device *dev)
> >>> @@ -1770,8 +1774,6 @@ static int ehea_set_mac_addr(struct net_device *dev, void *sa)
> >>>  
> >>>  	memcpy(dev->dev_addr, mac_addr->sa_data, dev->addr_len);
> >>>  
> >>> -	spin_lock(&ehea_bcmc_regs.lock);
> >>> -
> >>>  	/* Deregister old MAC in pHYP */
> >>>  	if (port->state == EHEA_PORT_UP) {
> >>>  		ret = ehea_broadcast_reg_helper(port, H_DEREG_BCMC);
> >>> @@ -1792,7 +1794,6 @@ static int ehea_set_mac_addr(struct net_device *dev, void *sa)
> >>>  
> >>>  out_upregs:
> >>>  	ehea_update_bcmc_registrations();
> >>> -	spin_unlock(&ehea_bcmc_regs.lock);
> >>>  out_free:
> >>>  	kfree(cb0);
> >>>  out:
> >>> @@ -1954,8 +1955,6 @@ static void ehea_set_multicast_list(struct net_device *dev)
> >>>  	}
> >>>  	ehea_promiscuous(dev, 0);
> >>>  
> >>> -	spin_lock(&ehea_bcmc_regs.lock);
> >>> -
> >>>  	if (dev->flags & IFF_ALLMULTI) {
> >>>  		ehea_allmulti(dev, 1);
> >>>  		goto out;
> >>> @@ -1985,7 +1984,6 @@ static void ehea_set_multicast_list(struct net_device *dev)
> >>>  	}
> >>>  out:
> >>>  	ehea_update_bcmc_registrations();
> >>> -	spin_unlock(&ehea_bcmc_regs.lock);
> >>>  	return;
> >>>  }
> >>>  
> >>> @@ -2466,8 +2464,6 @@ static int ehea_up(struct net_device *dev)
> >>>  	if (port->state == EHEA_PORT_UP)
> >>>  		return 0;
> >>>  
> >>> -	mutex_lock(&ehea_fw_handles.lock);
> >>> -
> >>>  	ret = ehea_port_res_setup(port, port->num_def_qps,
> >>>  				  port->num_add_tx_qps);
> >>>  	if (ret) {
> >>> @@ -2504,8 +2500,6 @@ static int ehea_up(struct net_device *dev)
> >>>  		}
> >>>  	}
> >>>  
> >>> -	spin_lock(&ehea_bcmc_regs.lock);
> >>> -
> >>>  	ret = ehea_broadcast_reg_helper(port, H_REG_BCMC);
> >>>  	if (ret) {
> >>>  		ret = -EIO;
> >>> @@ -2527,10 +2521,8 @@ out:
> >>>  		ehea_info("Failed starting %s. ret=%i", dev->name, ret);
> >>>  
> >>>  	ehea_update_bcmc_registrations();
> >>> -	spin_unlock(&ehea_bcmc_regs.lock);
> >>>  
> >>>  	ehea_update_firmware_handles();
> >>> -	mutex_unlock(&ehea_fw_handles.lock);
> >>>  
> >>>  	return ret;
> >>>  }
> >>> @@ -2580,9 +2572,6 @@ static int ehea_down(struct net_device *dev)
> >>>  	if (port->state == EHEA_PORT_DOWN)
> >>>  		return 0;
> >>>  
> >>> -	mutex_lock(&ehea_fw_handles.lock);
> >>> -
> >>> -	spin_lock(&ehea_bcmc_regs.lock);
> >>>  	ehea_drop_multicast_list(dev);
> >>>  	ehea_broadcast_reg_helper(port, H_DEREG_BCMC);
> >>>  
> >>> @@ -2591,7 +2580,6 @@ static int ehea_down(struct net_device *dev)
> >>>  	port->state = EHEA_PORT_DOWN;
> >>>  
> >>>  	ehea_update_bcmc_registrations();
> >>> -	spin_unlock(&ehea_bcmc_regs.lock);
> >>>  
> >>>  	ret = ehea_clean_all_portres(port);
> >>>  	if (ret)
> >>> @@ -2599,7 +2587,6 @@ static int ehea_down(struct net_device *dev)
> >>>  			  dev->name, ret);
> >>>  
> >>>  	ehea_update_firmware_handles();
> >>> -	mutex_unlock(&ehea_fw_handles.lock);
> >>>  
> >>>  	return ret;
> >>>  }
> >>> @@ -3378,7 +3365,6 @@ static int __devinit ehea_probe_adapter(struct of_device *dev,
> >>>  		ehea_error("Invalid ibmebus device probed");
> >>>  		return -EINVAL;
> >>>  	}
> >>> -	mutex_lock(&ehea_fw_handles.lock);
> >>>  
> >>>  	adapter = kzalloc(sizeof(*adapter), GFP_KERNEL);
> >>>  	if (!adapter) {
> >>> @@ -3462,7 +3448,6 @@ out_free_ad:
> >>>  
> >>>  out:
> >>>  	ehea_update_firmware_handles();
> >>> -	mutex_unlock(&ehea_fw_handles.lock);
> >>>  	return ret;
> >>>  }
> >>>  
> >>> @@ -3481,8 +3466,6 @@ static int __devexit ehea_remove(struct of_device *dev)
> >>>  
> >>>  	flush_scheduled_work();
> >>>  
> >>> -	mutex_lock(&ehea_fw_handles.lock);
> >>> -
> >>>  	ibmebus_free_irq(adapter->neq->attr.ist1, adapter);
> >>>  	tasklet_kill(&adapter->neq_tasklet);
> >>>  
> >>> @@ -3492,7 +3475,6 @@ static int __devexit ehea_remove(struct of_device *dev)
> >>>  	kfree(adapter);
> >>>  
> >>>  	ehea_update_firmware_handles();
> >>> -	mutex_unlock(&ehea_fw_handles.lock);
> >>>  
> >>>  	return 0;
> >>>  }
> >>
> >> _______________________________________________
> >> Linuxppc-dev mailing list
> >> Linuxppc-dev@...abs.org
> >> https://ozlabs.org/mailman/listinfo/linuxppc-dev
> >>
> 
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@...abs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-dev
> 
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