On Mon, Jan 08, 2024 at 06:24:55PM +0100, Marco Pagani wrote:
>
>
> On 2024-01-08 10:07, Xu Yilun wrote:
> > On Sat, Jan 06, 2024 at 12:15:26AM +0100, Marco Pagani wrote:
> >> Add a module owner field to the fpga_manager struct to take the
> >> low-level control module refcount instead of assuming that the parent
> >> device has a driver and using its owner pointer. The owner is now
> >> passed as an additional argument at registration time. To this end,
> >> the functions for registration have been modified to take an additional
> >> owner parameter and renamed to avoid conflicts. The old function names
> >> are now used for helper macros that automatically set the module that
> >> registers the fpga manager as the owner. This ensures compatibility
> >> with existing low-level control modules and reduces the chances of
> >> registering a manager without setting the owner.
> >>
> >> To detect when the owner module pointer becomes stale, set the mops
> >> pointer to null during fpga_mgr_unregister() and test it before taking
> >> the module's refcount. Use a mutex to protect against a crash that can
> >> happen if __fpga_mgr_get() gets suspended between testing the mops
> >> pointer and taking the refcount while the low-level module is being
> >> unloaded.
> >>
> >> Other changes: opportunistically move put_device() from __fpga_mgr_get()
> >> to fpga_mgr_get() and of_fpga_mgr_get() to improve code clarity since
> >> the device refcount in taken in these functions.
> >>
> >> Fixes: 654ba4cc0f3e ("fpga manager: ensure lifetime with of_fpga_mgr_get")
> >> Suggested-by: Xu Yilun <yilun.xu@xxxxxxxxx>
> >> Signed-off-by: Marco Pagani <marpagan@xxxxxxxxxx>
> >> ---
> >> drivers/fpga/fpga-mgr.c | 93 ++++++++++++++++++++++-------------
> >> include/linux/fpga/fpga-mgr.h | 80 +++++++++++++++++++++++++++---
> >> 2 files changed, 134 insertions(+), 39 deletions(-)
> >>
> >> diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
> >> index 06651389c592..d7bfbdfdf2fc 100644
> >> --- a/drivers/fpga/fpga-mgr.c
> >> +++ b/drivers/fpga/fpga-mgr.c
> >> @@ -664,20 +664,20 @@ static struct attribute *fpga_mgr_attrs[] = {
> >> };
> >> ATTRIBUTE_GROUPS(fpga_mgr);
> >>
> >> -static struct fpga_manager *__fpga_mgr_get(struct device *dev)
> >> +static struct fpga_manager *__fpga_mgr_get(struct device *mgr_dev)
> >> {
> >> struct fpga_manager *mgr;
> >>
> >> - mgr = to_fpga_manager(dev);
> >> + mgr = to_fpga_manager(mgr_dev);
> >>
> >> - if (!try_module_get(dev->parent->driver->owner))
> >> - goto err_dev;
> >> + mutex_lock(&mgr->mops_mutex);
> >>
> >> - return mgr;
> >> + if (!mgr->mops || !try_module_get(mgr->mops_owner))
> >
> > Why move the owner out of struct fpga_manager_ops? The owner within the
> > ops struct makes more sense to me, it better illustrates what the mutex
> > is protecting.
> >
>
> I think having the owner in fpga_manager_ops made sense when it was
> meant to be set while initializing the struct in the low-level module.
> However, since the owner is now passed as an argument and set at
> registration time, keeping it in the FPGA manager context seems more
> straightforward to me.
That's OK. But then why not directly check mops_owner here?
>
>
> >> + mgr = ERR_PTR(-ENODEV);
> >>
> >> -err_dev:
> >> - put_device(dev);
> >> - return ERR_PTR(-ENODEV);
> >> + mutex_unlock(&mgr->mops_mutex);
> >> +
> >> + return mgr;
> >> }
> >>
> >> static int fpga_mgr_dev_match(struct device *dev, const void *data)
> >> @@ -693,12 +693,18 @@ static int fpga_mgr_dev_match(struct device *dev, const void *data)
> >> */
> >> struct fpga_manager *fpga_mgr_get(struct device *dev)
> >> {
> >> - struct device *mgr_dev = class_find_device(&fpga_mgr_class, NULL, dev,
> >> - fpga_mgr_dev_match);
> >> + struct fpga_manager *mgr;
> >> + struct device *mgr_dev;
> >> +
> >> + mgr_dev = class_find_device(&fpga_mgr_class, NULL, dev, fpga_mgr_dev_match);
> >> if (!mgr_dev)
> >> return ERR_PTR(-ENODEV);
> >>
> >> - return __fpga_mgr_get(mgr_dev);
> >> + mgr = __fpga_mgr_get(mgr_dev);
> >> + if (IS_ERR(mgr))
> >> + put_device(mgr_dev);
> >> +
> >> + return mgr;
> >> }
> >> EXPORT_SYMBOL_GPL(fpga_mgr_get);
> >>
> >> @@ -711,13 +717,18 @@ EXPORT_SYMBOL_GPL(fpga_mgr_get);
> >> */
> >> struct fpga_manager *of_fpga_mgr_get(struct device_node *node)
> >> {
> >> - struct device *dev;
> >> + struct fpga_manager *mgr;
> >> + struct device *mgr_dev;
> >>
> >> - dev = class_find_device_by_of_node(&fpga_mgr_class, node);
> >> - if (!dev)
> >> + mgr_dev = class_find_device_by_of_node(&fpga_mgr_class, node);
> >> + if (!mgr_dev)
> >> return ERR_PTR(-ENODEV);
> >>
> >> - return __fpga_mgr_get(dev);
> >> + mgr = __fpga_mgr_get(mgr_dev);
> >> + if (IS_ERR(mgr))
> >> + put_device(mgr_dev);
> >> +
> >> + return mgr;
> >> }
> >> EXPORT_SYMBOL_GPL(of_fpga_mgr_get);
> >>
> >> @@ -727,7 +738,7 @@ EXPORT_SYMBOL_GPL(of_fpga_mgr_get);
> >> */
> >> void fpga_mgr_put(struct fpga_manager *mgr)
> >> {
> >> - module_put(mgr->dev.parent->driver->owner);
> >> + module_put(mgr->mops_owner);
> >> put_device(&mgr->dev);
> >> }
> >> EXPORT_SYMBOL_GPL(fpga_mgr_put);
> >> @@ -766,9 +777,10 @@ void fpga_mgr_unlock(struct fpga_manager *mgr)
> >> EXPORT_SYMBOL_GPL(fpga_mgr_unlock);
> >>
> >> /**
> >> - * fpga_mgr_register_full - create and register an FPGA Manager device
> >> + * __fpga_mgr_register_full - create and register an FPGA Manager device
> >> * @parent: fpga manager device from pdev
> >> * @info: parameters for fpga manager
> >> + * @owner: owner module containing the ops
> >> *
> >> * The caller of this function is responsible for calling fpga_mgr_unregister().
> >> * Using devm_fpga_mgr_register_full() instead is recommended.
> >> @@ -776,7 +788,8 @@ EXPORT_SYMBOL_GPL(fpga_mgr_unlock);
> >> * Return: pointer to struct fpga_manager pointer or ERR_PTR()
> >> */
> >> struct fpga_manager *
> >> -fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *info)
> >> +__fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *info,
> >> + struct module *owner)
> >> {
> >> const struct fpga_manager_ops *mops = info->mops;
> >> struct fpga_manager *mgr;
> >> @@ -803,6 +816,9 @@ fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *in
> >> }
> >>
> >> mutex_init(&mgr->ref_mutex);
> >> + mutex_init(&mgr->mops_mutex);
> >> +
> >> + mgr->mops_owner = owner;
> >>
> >> mgr->name = info->name;
> >> mgr->mops = info->mops;
> >> @@ -841,14 +857,15 @@ fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *in
> >>
> >> return ERR_PTR(ret);
> >> }
> >> -EXPORT_SYMBOL_GPL(fpga_mgr_register_full);
> >> +EXPORT_SYMBOL_GPL(__fpga_mgr_register_full);
> >>
> >> /**
> >> - * fpga_mgr_register - create and register an FPGA Manager device
> >> + * __fpga_mgr_register - create and register an FPGA Manager device
> >> * @parent: fpga manager device from pdev
> >> * @name: fpga manager name
> >> * @mops: pointer to structure of fpga manager ops
> >> * @priv: fpga manager private data
> >> + * @owner: owner module containing the ops
> >> *
> >> * The caller of this function is responsible for calling fpga_mgr_unregister().
> >> * Using devm_fpga_mgr_register() instead is recommended. This simple
> >> @@ -859,8 +876,8 @@ EXPORT_SYMBOL_GPL(fpga_mgr_register_full);
> >> * Return: pointer to struct fpga_manager pointer or ERR_PTR()
> >> */
> >> struct fpga_manager *
> >> -fpga_mgr_register(struct device *parent, const char *name,
> >> - const struct fpga_manager_ops *mops, void *priv)
> >> +__fpga_mgr_register(struct device *parent, const char *name,
> >> + const struct fpga_manager_ops *mops, void *priv, struct module *owner)
> >> {
> >> struct fpga_manager_info info = { 0 };
> >>
> >> @@ -868,9 +885,9 @@ fpga_mgr_register(struct device *parent, const char *name,
> >> info.mops = mops;
> >> info.priv = priv;
> >>
> >> - return fpga_mgr_register_full(parent, &info);
> >> + return __fpga_mgr_register_full(parent, &info, owner);
> >> }
> >> -EXPORT_SYMBOL_GPL(fpga_mgr_register);
> >> +EXPORT_SYMBOL_GPL(__fpga_mgr_register);
> >>
> >> /**
> >> * fpga_mgr_unregister - unregister an FPGA manager
> >> @@ -888,6 +905,12 @@ void fpga_mgr_unregister(struct fpga_manager *mgr)
> >> */
> >> fpga_mgr_fpga_remove(mgr);
> >>
> >> + mutex_lock(&mgr->mops_mutex);
> >> +
> >> + mgr->mops = NULL;
Same here, is it better set mgr->mops_owner = NULL?
> >> +
> >> + mutex_unlock(&mgr->mops_mutex);
> >> +
> >> device_unregister(&mgr->dev);
> >> }
> >> EXPORT_SYMBOL_GPL(fpga_mgr_unregister);
> >> @@ -900,9 +923,10 @@ static void devm_fpga_mgr_unregister(struct device *dev, void *res)
> >> }
> >>
> >> /**
> >> - * devm_fpga_mgr_register_full - resource managed variant of fpga_mgr_register()
> >> + * __devm_fpga_mgr_register_full - resource managed variant of fpga_mgr_register()
> >> * @parent: fpga manager device from pdev
> >> * @info: parameters for fpga manager
> >> + * @owner: owner module containing the ops
> >> *
> >> * Return: fpga manager pointer on success, negative error code otherwise.
> >> *
> >> @@ -910,7 +934,8 @@ static void devm_fpga_mgr_unregister(struct device *dev, void *res)
> >> * function will be called automatically when the managing device is detached.
> >> */
> >> struct fpga_manager *
> >> -devm_fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *info)
> >> +__devm_fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *info,
> >> + struct module *owner)
> >> {
> >> struct fpga_mgr_devres *dr;
> >> struct fpga_manager *mgr;
> >> @@ -919,7 +944,7 @@ devm_fpga_mgr_register_full(struct device *parent, const struct fpga_manager_inf
> >> if (!dr)
> >> return ERR_PTR(-ENOMEM);
> >>
> >> - mgr = fpga_mgr_register_full(parent, info);
> >> + mgr = __fpga_mgr_register_full(parent, info, owner);
> >> if (IS_ERR(mgr)) {
> >> devres_free(dr);
> >> return mgr;
> >> @@ -930,14 +955,15 @@ devm_fpga_mgr_register_full(struct device *parent, const struct fpga_manager_inf
> >>
> >> return mgr;
> >> }
> >> -EXPORT_SYMBOL_GPL(devm_fpga_mgr_register_full);
> >> +EXPORT_SYMBOL_GPL(__devm_fpga_mgr_register_full);
> >>
> >> /**
> >> - * devm_fpga_mgr_register - resource managed variant of fpga_mgr_register()
> >> + * __devm_fpga_mgr_register - resource managed variant of fpga_mgr_register()
> >> * @parent: fpga manager device from pdev
> >> * @name: fpga manager name
> >> * @mops: pointer to structure of fpga manager ops
> >> * @priv: fpga manager private data
> >> + * @owner: owner module containing the ops
> >> *
> >> * Return: fpga manager pointer on success, negative error code otherwise.
> >> *
> >> @@ -946,8 +972,9 @@ EXPORT_SYMBOL_GPL(devm_fpga_mgr_register_full);
> >> * device is detached.
> >> */
> >> struct fpga_manager *
> >> -devm_fpga_mgr_register(struct device *parent, const char *name,
> >> - const struct fpga_manager_ops *mops, void *priv)
> >> +__devm_fpga_mgr_register(struct device *parent, const char *name,
> >> + const struct fpga_manager_ops *mops, void *priv,
> >> + struct module *owner)
> >> {
> >> struct fpga_manager_info info = { 0 };
> >>
> >> @@ -955,9 +982,9 @@ devm_fpga_mgr_register(struct device *parent, const char *name,
> >> info.mops = mops;
> >> info.priv = priv;
> >>
> >> - return devm_fpga_mgr_register_full(parent, &info);
> >> + return __devm_fpga_mgr_register_full(parent, &info, owner);
> >> }
> >> -EXPORT_SYMBOL_GPL(devm_fpga_mgr_register);
> >> +EXPORT_SYMBOL_GPL(__devm_fpga_mgr_register);
> >>
> >> static void fpga_mgr_dev_release(struct device *dev)
> >> {
> >> diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h
> >> index 54f63459efd6..967540311462 100644
> >> --- a/include/linux/fpga/fpga-mgr.h
> >> +++ b/include/linux/fpga/fpga-mgr.h
> >> @@ -201,6 +201,8 @@ struct fpga_manager_ops {
> >> * @state: state of fpga manager
> >> * @compat_id: FPGA manager id for compatibility check.
> >> * @mops: pointer to struct of fpga manager ops
> >> + * @mops_mutex: protects mops from low-level module removal
Same here, change the doc if needed.
> >> + * @mops_owner: module containing the mops
> >> * @priv: low level driver private date
> >> */
> >> struct fpga_manager {
> >> @@ -210,6 +212,8 @@ struct fpga_manager {
> >> enum fpga_mgr_states state;
> >> struct fpga_compat_id *compat_id;
> >> const struct fpga_manager_ops *mops;
> >> + struct mutex mops_mutex;
> >> + struct module *mops_owner;
> >> void *priv;
> >> };
> >>
> >> @@ -222,6 +226,7 @@ void fpga_image_info_free(struct fpga_image_info *info);
> >> int fpga_mgr_load(struct fpga_manager *mgr, struct fpga_image_info *info);
> >>
> >> int fpga_mgr_lock(struct fpga_manager *mgr);
> >> +
> >
> > Why adding a line?
> >
>
> I'll remove the line.
>
> >> void fpga_mgr_unlock(struct fpga_manager *mgr);
> >>
> >> struct fpga_manager *of_fpga_mgr_get(struct device_node *node);
> >> @@ -230,18 +235,81 @@ struct fpga_manager *fpga_mgr_get(struct device *dev);
> >>
> >> void fpga_mgr_put(struct fpga_manager *mgr);
> >>
> >> +/**
> >> + * fpga_mgr_register_full - create and register an FPGA Manager device
> >> + * @parent: fpga manager device from pdev
> >> + * @info: parameters for fpga manager
> >> + *
> >> + * The caller of this function is responsible for calling fpga_mgr_unregister().
> >> + * Using devm_fpga_mgr_register_full() instead is recommended.
> >> + *
> >> + * Return: pointer to struct fpga_manager pointer or ERR_PTR()
> >> + */
> >
> > No need to duplicate the doc, just remove it.
> > Same for the rest of code.
>
> Do you mean keeping the kernel-doc comments only for the __fpga_mgr_*
> functions in fpga-mgr.c?
>
> >
> >> +#define fpga_mgr_register_full(parent, info) \
> >> + __fpga_mgr_register_full(parent, info, THIS_MODULE)
> >> +
> >
> > Delete the line, and ...
> >
> >> struct fpga_manager *
> >> -fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *info);
> >> +__fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *info,
> >> + struct module *owner);
> >
> > Add a line here, to make the related functions packed.
> > Same for the rest of code.
>
> Do you prefer having the macro just above the function prototype? Like:
>
> #define devm_fpga_mgr_register(parent, name, mops, priv) \
> __devm_fpga_mgr_register(parent, name, mops, priv, THIS_MODULE)
> struct fpga_manager *
> __devm_fpga_mgr_register(struct device *parent, const char *name,
> const struct fpga_manager_ops *mops, void *priv,
> struct module *owner);
Yes, that's it.
Thanks,
Yilun
>
> >
> >> +/**
> >> + * fpga_mgr_register - create and register an FPGA Manager device
> >> + * @parent: fpga manager device from pdev
> >> + * @name: fpga manager name
> >> + * @mops: pointer to structure of fpga manager ops
> >> + * @priv: fpga manager private data
> >> + *
> >> + * The caller of this function is responsible for calling fpga_mgr_unregister().
> >> + * Using devm_fpga_mgr_register() instead is recommended. This simple
> >> + * version of the register function should be sufficient for most users. The
> >> + * fpga_mgr_register_full() function is available for users that need to pass
> >> + * additional, optional parameters.
> >> + *
> >> + * Return: pointer to struct fpga_manager pointer or ERR_PTR()
> >> + */
> >> +#define fpga_mgr_register(parent, name, mops, priv) \
> >> + __fpga_mgr_register(parent, name, mops, priv, THIS_MODULE)
> >>
> >> struct fpga_manager *
> >> -fpga_mgr_register(struct device *parent, const char *name,
> >> - const struct fpga_manager_ops *mops, void *priv);
> >> +__fpga_mgr_register(struct device *parent, const char *name,
> >> + const struct fpga_manager_ops *mops, void *priv, struct module *owner);
> >> +
> >> void fpga_mgr_unregister(struct fpga_manager *mgr);
> >>
> >> +/**
> >> + * devm_fpga_mgr_register_full - resource managed variant of fpga_mgr_register()
> >> + * @parent: fpga manager device from pdev
> >> + * @info: parameters for fpga manager
> >> + *
> >> + * Return: fpga manager pointer on success, negative error code otherwise.
> >> + *
> >> + * This is the devres variant of fpga_mgr_register_full() for which the unregister
> >> + * function will be called automatically when the managing device is detached.
> >> + */
> >> +#define devm_fpga_mgr_register_full(parent, info) \
> >> + __devm_fpga_mgr_register_full(parent, info, THIS_MODULE)
> >> +
> >> struct fpga_manager *
> >> -devm_fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *info);
> >> +__devm_fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *info,
> >> + struct module *owner);
> >> +/**
> >> + * devm_fpga_mgr_register - resource managed variant of fpga_mgr_register()
> >> + * @parent: fpga manager device from pdev
> >> + * @name: fpga manager name
> >> + * @mops: pointer to structure of fpga manager ops
> >> + * @priv: fpga manager private data
> >> + *
> >> + * Return: fpga manager pointer on success, negative error code otherwise.
> >> + *
> >> + * This is the devres variant of fpga_mgr_register() for which the
> >> + * unregister function will be called automatically when the managing
> >> + * device is detached.
> >> + */
> >> +#define devm_fpga_mgr_register(parent, name, mops, priv) \
> >> + __devm_fpga_mgr_register(parent, name, mops, priv, THIS_MODULE)
> >> +
> >> struct fpga_manager *
> >> -devm_fpga_mgr_register(struct device *parent, const char *name,
> >> - const struct fpga_manager_ops *mops, void *priv);
> >> +__devm_fpga_mgr_register(struct device *parent, const char *name,
> >> + const struct fpga_manager_ops *mops, void *priv,
> >> + struct module *owner);
> >>
> >> #endif /*_LINUX_FPGA_MGR_H */
> >> --
> >> 2.43.0
> >>
> >>
> >
>
