On Thu, 2010-10-28 at 00:13 +0800, Corey Minyard wrote:
> I think you miss the point of a refcount. The refcount is to keep the
> data structure around even if the device has gone away, so that any
> users may not crash. Just having a counter in the IPMI structure and
> then decrementing the device refcount is not going to accomplish anything.
>
> And you don't really need to refcount the IPMI structure. (And if you
> did, you would need to use a refcount structure and you would need to
> keep from freeing the IPMI structure until the refcount went to zero.)
> You just need to increment the refcount on the device structure, and
> whoever gets the device structure needs to be responsible for
> decrementing it's refcount.
Yes. After the copy mechanism is used, it is unnecessary to use the
refcount to protect the corresponding data structure.
In fact the purpose of adding another one refcount is to add/decrease
the refcount of dev in course of calling the function of
ipmi_get_smi_info/ipmi_put_smi_info.
But after I look at the smi_watcher mechanism, I find that the
refcount of dev is not released correctly in the following case.
Step 1: Other driver registers one smi_watcher and the
ipmi_get_smi_info is called in the new_smi callback function. (And the
driver will use the dev pointer before the ipmi_put_smi_info is
called).
Step 2: for any reason, the IPMI device will be unregistered by calling
cleanup_one_si. This function will remove it from the IPMI device list
firstly and then call the smi_gone for every smi_watcher.
Step 3: the ipmi_put_smi_info is called in smi_gone callback function.
In such case the ipmi_put_smi_info can't find the corresponding IPMI
device based on the given if_num and can't release the pointer of dev.
But after adding another refcount, we can handle the above scenario. At
the same time even when the ipmi_put_smi_info is not called by the
caller, it still can work.
Not sure whether the above thought is redundant?
> I'd also prefer to not have a struct ipmi_smi_info in the IPMI data
> structure. Just pull the data from existing sources.
At most cases the requirement is different for the different addr source
type. If we don't put the ipmi_smi_info in the IPMI data structure, I am
afraid that we will have to fill the corresponding info based on the
addr source type. Maybe it will be more complex.
Thanks.
Yakui
>
> -corey
>
> On 10/26/2010 04:14 AM, yakui.zhao@xxxxxxxxx wrote:
> > From: Zhao Yakui<yakui.zhao@xxxxxxxxx>
> >
> > The IPMI smi_watcher will be used to catch the IPMI interface as they come or go.
> > In order to communicate with the correct IPMI device, it should be confirmed
> > whether it is what we wanted especially on the system with multiple IPMI
> > devices. But the new_smi callback function of smi_watcher provides very
> > limited info(only the interface number and dev pointer) and there is no
> > detailed info about the low level interface. For example: which mechansim
> > registers the IPMI interface(ACPI, PCI, DMI and so on).
> >
> > This is to add one interface that can get more info of low-level IPMI
> > device. For example: the ACPI device handle will be returned for the pnp_acpi
> > IPMI device.
> >
> > Signed-off-by: Zhao Yakui<yakui.zhao@xxxxxxxxx>
> > ---
> > drivers/char/ipmi/ipmi_msghandler.c | 46 ++++++++++++++++++++++++++++++++
> > drivers/char/ipmi/ipmi_si_intf.c | 49 +++++++++++++++++++++++++++++++---
> > include/linux/ipmi.h | 29 ++++++++++++++++++++
> > include/linux/ipmi_smi.h | 8 +++++
> > 4 files changed, 127 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
> > index 4f3f8c9..e323edb 100644
> > --- a/drivers/char/ipmi/ipmi_msghandler.c
> > +++ b/drivers/char/ipmi/ipmi_msghandler.c
> > @@ -970,6 +970,52 @@ out_kfree:
> > }
> > EXPORT_SYMBOL(ipmi_create_user);
> >
> > +int ipmi_get_smi_info(int if_num, struct ipmi_smi_info *data)
> > +{
> > + int rv = 0;
> > + ipmi_smi_t intf;
> > + struct ipmi_smi_handlers *handlers;
> > +
> > + mutex_lock(&ipmi_interfaces_mutex);
> > + list_for_each_entry_rcu(intf,&ipmi_interfaces, link) {
> > + if (intf->intf_num == if_num)
> > + goto found;
> > + }
> > + /* Not found, return an error */
> > + rv = -EINVAL;
> > + mutex_unlock(&ipmi_interfaces_mutex);
> > + return rv;
> > +
> > +found:
> > + handlers = intf->handlers;
> > + rv = handlers->get_smi_info(intf->send_info, data);
> > + mutex_unlock(&ipmi_interfaces_mutex);
> > +
> > + return rv;
> > +}
> > +EXPORT_SYMBOL(ipmi_get_smi_info);
> > +
> > +void ipmi_put_smi_info(int if_num)
> > +{
> > + ipmi_smi_t intf;
> > + struct ipmi_smi_handlers *handlers;
> > +
> > + mutex_lock(&ipmi_interfaces_mutex);
> > + list_for_each_entry_rcu(intf,&ipmi_interfaces, link) {
> > + if (intf->intf_num == if_num)
> > + goto found;
> > + }
> > + /* Not found, return */
> > + mutex_unlock(&ipmi_interfaces_mutex);
> > + return;
> > +
> > +found:
> > + handlers = intf->handlers;
> > + handlers->put_smi_info(intf->send_info);
> > + mutex_unlock(&ipmi_interfaces_mutex);
> > +}
> > +EXPORT_SYMBOL(ipmi_put_smi_info);
> > +
> > static void free_user(struct kref *ref)
> > {
> > ipmi_user_t user = container_of(ref, struct ipmi_user, refcount);
> > diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
> > index 7bd7c45..d313018 100644
> > --- a/drivers/char/ipmi/ipmi_si_intf.c
> > +++ b/drivers/char/ipmi/ipmi_si_intf.c
> > @@ -57,6 +57,7 @@
> > #include<asm/irq.h>
> > #include<linux/interrupt.h>
> > #include<linux/rcupdate.h>
> > +#include<linux/ipmi.h>
> > #include<linux/ipmi_smi.h>
> > #include<asm/io.h>
> > #include "ipmi_si_sm.h"
> > @@ -107,10 +108,6 @@ enum si_type {
> > };
> > static char *si_to_str[] = { "kcs", "smic", "bt" };
> >
> > -enum ipmi_addr_src {
> > - SI_INVALID = 0, SI_HOTMOD, SI_HARDCODED, SI_SPMI, SI_ACPI, SI_SMBIOS,
> > - SI_PCI, SI_DEVICETREE, SI_DEFAULT
> > -};
> > static char *ipmi_addr_src_to_str[] = { NULL, "hotmod", "hardcoded", "SPMI",
> > "ACPI", "SMBIOS", "PCI",
> > "device-tree", "default" };
> > @@ -291,6 +288,12 @@ struct smi_info {
> > struct task_struct *thread;
> >
> > struct list_head link;
> > + /*
> > + * Count the refcount of smi_data->dev related with the function
> > + * of ipmi_get_smi_info/ipmi_put_smi_info.
> > + */
> > + atomic_t smi_info_ref;
> > + struct ipmi_smi_info smi_data;
> > };
> >
> > #define smi_inc_stat(smi, stat) \
> > @@ -1186,6 +1189,27 @@ static int smi_start_processing(void *send_info,
> > return 0;
> > }
> >
> > +static int get_smi_info(void *send_info, struct ipmi_smi_info *data)
> > +{
> > + struct smi_info *new_smi = send_info;
> > + struct ipmi_smi_info *smi_data =&new_smi->smi_data;
> > +
> > + get_device(new_smi->dev);
> > + memcpy(data, smi_data, sizeof(*smi_data));
> > + smi_data->addr_src = new_smi->addr_source;
> > + atomic_inc(&new_smi->smi_info_ref);
> > +
> > + return 0;
> > +}
> > +
> > +static void put_smi_info(void *send_info)
> > +{
> > + struct smi_info *new_smi = send_info;
> > +
> > + put_device(new_smi->dev);
> > + atomic_dec(&new_smi->smi_info_ref);
> > +}
> > +
> > static void set_maintenance_mode(void *send_info, int enable)
> > {
> > struct smi_info *smi_info = send_info;
> > @@ -1197,6 +1221,8 @@ static void set_maintenance_mode(void *send_info, int enable)
> > static struct ipmi_smi_handlers handlers = {
> > .owner = THIS_MODULE,
> > .start_processing = smi_start_processing,
> > + .get_smi_info = get_smi_info,
> > + .put_smi_info = put_smi_info,
> > .sender = sender,
> > .request_events = request_events,
> > .set_maintenance_mode = set_maintenance_mode,
> > @@ -2143,6 +2169,8 @@ static int __devinit ipmi_pnp_probe(struct pnp_dev *dev,
> > return -ENOMEM;
> >
> > info->addr_source = SI_ACPI;
> > + info->smi_data.addr_info.acpi_info.acpi_handle =
> > + acpi_dev->handle;
> > printk(KERN_INFO PFX "probing via ACPI\n");
> >
> > handle = acpi_dev->handle;
> > @@ -3092,6 +3120,7 @@ static int try_smi_init(struct smi_info *new_smi)
> > {
> > int rv = 0;
> > int i;
> > + struct ipmi_smi_info *smi_data;
> >
> > printk(KERN_INFO PFX "Trying %s-specified %s state"
> > " machine at %s address 0x%lx, slave address 0x%x,"
> > @@ -3255,6 +3284,9 @@ static int try_smi_init(struct smi_info *new_smi)
> >
> > dev_info(new_smi->dev, "IPMI %s interface initialized\n",
> > si_to_str[new_smi->si_type]);
> > + smi_data =&new_smi->smi_data;
> > + smi_data->dev = new_smi->dev;
> > + atomic_set(&new_smi->smi_info_ref, 0);
> >
> > return 0;
> >
> > @@ -3501,7 +3533,14 @@ static void cleanup_one_si(struct smi_info *to_clean)
> > printk(KERN_ERR PFX "Unable to unregister device: errno=%d\n",
> > rv);
> > }
> > -
> > + /* maybe the caller doesn't release the refcount of dev, which is
> > + * increased by calling the function of ipmi_get_smi_info. So try
> > + * to help it.
> > + */
> > + while (atomic_read(&to_clean->smi_info_ref)) {
> > + put_device(to_clean->dev);
> > + atomic_dec(&to_clean->smi_info_ref);
> > + }
> > if (to_clean->handlers)
> > to_clean->handlers->cleanup(to_clean->si_sm);
> >
> > diff --git a/include/linux/ipmi.h b/include/linux/ipmi.h
> > index 65aae34..9a0c72e 100644
> > --- a/include/linux/ipmi.h
> > +++ b/include/linux/ipmi.h
> > @@ -454,6 +454,35 @@ unsigned int ipmi_addr_length(int addr_type);
> > /* Validate that the given IPMI address is valid. */
> > int ipmi_validate_addr(struct ipmi_addr *addr, int len);
> >
> > +enum ipmi_addr_src {
> > + SI_INVALID = 0, SI_HOTMOD, SI_HARDCODED, SI_SPMI, SI_ACPI, SI_SMBIOS,
> > + SI_PCI, SI_DEVICETREE, SI_DEFAULT
> > +};
> > +struct ipmi_smi_info {
> > + enum ipmi_addr_src addr_src;
> > + struct device *dev;
> > + /*
> > + * The addr_info can provide more detailed info of one IPMI device.
> > + * Now only SI_ACPI info is provided. And it depends on the SI_ACPI
> > + * address type. If the info is required for other address type, please
> > + * add it.
> > + */
> > + union {
> > + /* the acpi_info element is defined for the SI_ACPI
> > + * address type
> > + */
> > + struct {
> > + void *acpi_handle;
> > + } acpi_info;
> > + } addr_info;
> > +};
> > +
> > +/* This is to get the private info of ipmi_smi_t */
> > +extern int ipmi_get_smi_info(int if_num, struct ipmi_smi_info *data);
> > +/* This is to decrease refcount of dev added in the function of
> > + * ipmi_get_smi_info
> > + */
> > +extern void ipmi_put_smi_info(int if_num);
> > #endif /* __KERNEL__ */
> >
> >
> > diff --git a/include/linux/ipmi_smi.h b/include/linux/ipmi_smi.h
> > index 4b48318..b99942d 100644
> > --- a/include/linux/ipmi_smi.h
> > +++ b/include/linux/ipmi_smi.h
> > @@ -86,6 +86,14 @@ struct ipmi_smi_handlers {
> > int (*start_processing)(void *send_info,
> > ipmi_smi_t new_intf);
> >
> > + /*
> > + * Get the detailed private info of the low level interface and store
> > + * it into the structure of ipmi_smi_data. For example: the
> > + * ACPI device handle will be returned for the pnp_acpi IPMI device.
> > + */
> > + int (*get_smi_info)(void *send_info, struct ipmi_smi_info *data);
> > +
> > + void (*put_smi_info)(void *send_info);
> > /* Called to enqueue an SMI message to be sent. This
> > operation is not allowed to fail. If an error occurs, it
> > should report back the error in a received message. It may
> >
>
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