Am Mittwoch, dem 12.06.2024 um 12:00 +0200 schrieb Andrea Calabrese:
> Hi Lucas,
>
> On 12/06/2024 11:26, Lucas Stach wrote:
> > Am Dienstag, dem 11.06.2024 um 11:37 +0200 schrieb Andrea Calabrese:
> > > Code refactoring using the recent guard and scoped_guard macros
> > > for automatic cleanup of the spinlocks. This does not change the
> > > effective behaviour of the kernel, but guarantees a cleaned-up exit from
> > > each lock, automatically avoiding potential deadlocks.
> > >
> > > Signed-off-by: Andrea Calabrese <andrea.calabrese@xxxxxxxxxxxxxxxxxxxx>
> > >
> > > ---
> > > Changed commit message from V2. Also changed title, shortened the file
> > > name.
> > >
> > > diff --git a/drivers/base/devres.c b/drivers/base/devres.c
> > > index 3df0025d12aa..a98720e0cb2b 100644
> > > --- a/drivers/base/devres.c
> > > +++ b/drivers/base/devres.c
> > > @@ -194,14 +194,12 @@ void devres_for_each_res(struct device *dev, dr_release_t release,
> > > {
> > > struct devres_node *node;
> > > struct devres_node *tmp;
> > > - unsigned long flags;
> > >
> > > if (!fn)
> > > return;
> > >
> > > - spin_lock_irqsave(&dev->devres_lock, flags);
> > > - list_for_each_entry_safe_reverse(node, tmp,
> > > - &dev->devres_head, entry) {
> > > + guard(spinlock)(&dev->devres_lock);
> > This is not equivalent to the current code. You are dropping the
> > _irqsave part of the locking scheme, totally changing the semantics
> > here. This issue is present in multiple places in this patch.
> >
> > Regards,
> > Lucas
> I don't see where is the issue here, as I am using both guard and
> scoped_guard similarly to how they are used in
> drivers/gpio/gpiolib-cdev.c, which I took as a reference for the usage
> of the construct. If so, probably we may both be using it wrong.
Blindly copying from a another subsystem, which may have a very
different locking architecture, is never a good idea. Please educate
yourself about the difference between spin_lock, spin_lock_irq and
spin_lock_irqsave.
You need to use guard(spinlock_irqsave) here for the new code to be
equivalent to the code you are removing. Since this is supposed to be a
cleanup/simplification the new code _needs_ to keep the semantics of
the original code. You can not hide a total change in locking
architecture in a change like that.
Regards,
Lucas
> > > + list_for_each_entry_safe_reverse(node, tmp, &dev->devres_head, entry) {
> > > struct devres *dr = container_of(node, struct devres, node);
> > >
> > > if (node->release != release)
> > > @@ -210,7 +208,6 @@ void devres_for_each_res(struct device *dev, dr_release_t release,
> > > continue;
> > > fn(dev, dr->data, data);
> > > }
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > > }
> > > EXPORT_SYMBOL_GPL(devres_for_each_res);
> > >
> > > @@ -243,11 +240,9 @@ EXPORT_SYMBOL_GPL(devres_free);
> > > void devres_add(struct device *dev, void *res)
> > > {
> > > struct devres *dr = container_of(res, struct devres, data);
> > > - unsigned long flags;
> > >
> > > - spin_lock_irqsave(&dev->devres_lock, flags);
> > > + guard(spinlock)(&dev->devres_lock);
> > > add_dr(dev, &dr->node);
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > > }
> > > EXPORT_SYMBOL_GPL(devres_add);
> > >
> > > @@ -287,11 +282,8 @@ void * devres_find(struct device *dev, dr_release_t release,
> > > dr_match_t match, void *match_data)
> > > {
> > > struct devres *dr;
> > > - unsigned long flags;
> > > -
> > > - spin_lock_irqsave(&dev->devres_lock, flags);
> > > + guard(spinlock)(&dev->devres_lock);
> > > dr = find_dr(dev, release, match, match_data);
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > >
> > > if (dr)
> > > return dr->data;
> > > @@ -318,16 +310,14 @@ void * devres_get(struct device *dev, void *new_res,
> > > {
> > > struct devres *new_dr = container_of(new_res, struct devres, data);
> > > struct devres *dr;
> > > - unsigned long flags;
> > > -
> > > - spin_lock_irqsave(&dev->devres_lock, flags);
> > > - dr = find_dr(dev, new_dr->node.release, match, match_data);
> > > - if (!dr) {
> > > - add_dr(dev, &new_dr->node);
> > > - dr = new_dr;
> > > - new_res = NULL;
> > > + scoped_guard(spinlock, &dev->devres_lock) {
> > > + dr = find_dr(dev, new_dr->node.release, match, match_data);
> > > + if (!dr) {
> > > + add_dr(dev, &new_dr->node);
> > > + dr = new_dr;
> > > + new_res = NULL;
> > > + }
> > > }
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > > devres_free(new_res);
> > >
> > > return dr->data;
> > > @@ -353,15 +343,13 @@ void * devres_remove(struct device *dev, dr_release_t release,
> > > dr_match_t match, void *match_data)
> > > {
> > > struct devres *dr;
> > > - unsigned long flags;
> > > -
> > > - spin_lock_irqsave(&dev->devres_lock, flags);
> > > - dr = find_dr(dev, release, match, match_data);
> > > - if (dr) {
> > > - list_del_init(&dr->node.entry);
> > > - devres_log(dev, &dr->node, "REM");
> > > + scoped_guard(spinlock, &dev->devres_lock) {
> > > + dr = find_dr(dev, release, match, match_data);
> > > + if (dr) {
> > > + list_del_init(&dr->node.entry);
> > > + devres_log(dev, &dr->node, "REM");
> > > + }
> > > }
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > >
> > > if (dr)
> > > return dr->data;
> > > @@ -516,7 +504,6 @@ static void release_nodes(struct device *dev, struct list_head *todo)
> > > */
> > > int devres_release_all(struct device *dev)
> > > {
> > > - unsigned long flags;
> > > LIST_HEAD(todo);
> > > int cnt;
> > >
> > > @@ -528,9 +515,9 @@ int devres_release_all(struct device *dev)
> > > if (list_empty(&dev->devres_head))
> > > return 0;
> > >
> > > - spin_lock_irqsave(&dev->devres_lock, flags);
> > > - cnt = remove_nodes(dev, dev->devres_head.next, &dev->devres_head, &todo);
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > > + scoped_guard(spinlock, &dev->devres_lock) {
> > > + cnt = remove_nodes(dev, dev->devres_head.next, &dev->devres_head, &todo);
> > > + }
> > >
> > > release_nodes(dev, &todo);
> > > return cnt;
> > > @@ -552,7 +539,6 @@ int devres_release_all(struct device *dev)
> > > void * devres_open_group(struct device *dev, void *id, gfp_t gfp)
> > > {
> > > struct devres_group *grp;
> > > - unsigned long flags;
> > >
> > > grp = kmalloc(sizeof(*grp), gfp);
> > > if (unlikely(!grp))
> > > @@ -568,9 +554,8 @@ void * devres_open_group(struct device *dev, void *id, gfp_t gfp)
> > > if (id)
> > > grp->id = id;
> > >
> > > - spin_lock_irqsave(&dev->devres_lock, flags);
> > > + guard(spinlock)(&dev->devres_lock);
> > > add_dr(dev, &grp->node[0]);
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > > return grp->id;
> > > }
> > > EXPORT_SYMBOL_GPL(devres_open_group);
> > > @@ -609,17 +594,14 @@ static struct devres_group * find_group(struct device *dev, void *id)
> > > void devres_close_group(struct device *dev, void *id)
> > > {
> > > struct devres_group *grp;
> > > - unsigned long flags;
> > >
> > > - spin_lock_irqsave(&dev->devres_lock, flags);
> > > + guard(spinlock)(&dev->devres_lock);
> > >
> > > grp = find_group(dev, id);
> > > if (grp)
> > > add_dr(dev, &grp->node[1]);
> > > else
> > > WARN_ON(1);
> > > -
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > > }
> > > EXPORT_SYMBOL_GPL(devres_close_group);
> > >
> > > @@ -635,19 +617,16 @@ EXPORT_SYMBOL_GPL(devres_close_group);
> > > void devres_remove_group(struct device *dev, void *id)
> > > {
> > > struct devres_group *grp;
> > > - unsigned long flags;
> > > -
> > > - spin_lock_irqsave(&dev->devres_lock, flags);
> > > -
> > > - grp = find_group(dev, id);
> > > - if (grp) {
> > > - list_del_init(&grp->node[0].entry);
> > > - list_del_init(&grp->node[1].entry);
> > > - devres_log(dev, &grp->node[0], "REM");
> > > - } else
> > > - WARN_ON(1);
> > >
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > > + scoped_guard(spinlock, &dev->devres_lock) {
> > > + grp = find_group(dev, id);
> > > + if (grp) {
> > > + list_del_init(&grp->node[0].entry);
> > > + list_del_init(&grp->node[1].entry);
> > > + devres_log(dev, &grp->node[0], "REM");
> > > + } else
> > > + WARN_ON(1);
> > > + }
> > >
> > > kfree(grp);
> > > }
> > > @@ -668,11 +647,10 @@ EXPORT_SYMBOL_GPL(devres_remove_group);
> > > int devres_release_group(struct device *dev, void *id)
> > > {
> > > struct devres_group *grp;
> > > - unsigned long flags;
> > > LIST_HEAD(todo);
> > > int cnt = 0;
> > >
> > > - spin_lock_irqsave(&dev->devres_lock, flags);
> > > + guard(spinlock)(&dev->devres_lock);
> > >
> > > grp = find_group(dev, id);
> > > if (grp) {
> > > @@ -683,12 +661,9 @@ int devres_release_group(struct device *dev, void *id)
> > > end = grp->node[1].entry.next;
> > >
> > > cnt = remove_nodes(dev, first, end, &todo);
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > > -
> > > release_nodes(dev, &todo);
> > > } else {
> > > WARN_ON(1);
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > > }
> > >
> > > return cnt;
> > > @@ -860,7 +835,6 @@ void *devm_krealloc(struct device *dev, void *ptr, size_t new_size, gfp_t gfp)
> > > {
> > > size_t total_new_size, total_old_size;
> > > struct devres *old_dr, *new_dr;
> > > - unsigned long flags;
> > >
> > > if (unlikely(!new_size)) {
> > > devm_kfree(dev, ptr);
> > > @@ -906,20 +880,17 @@ void *devm_krealloc(struct device *dev, void *ptr, size_t new_size, gfp_t gfp)
> > > * The spinlock protects the linked list against concurrent
> > > * modifications but not the resource itself.
> > > */
> > > - spin_lock_irqsave(&dev->devres_lock, flags);
> > > + scoped_guard(spinlock, &dev->devres_lock) {
> > > + old_dr = find_dr(dev, devm_kmalloc_release, devm_kmalloc_match, ptr);
> > > + if (!old_dr) {
> > > + kfree(new_dr);
> > > + WARN(1, "Memory chunk not managed or managed by a different device.");
> > > + return NULL;
> > > + }
> > >
> > > - old_dr = find_dr(dev, devm_kmalloc_release, devm_kmalloc_match, ptr);
> > > - if (!old_dr) {
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > > - kfree(new_dr);
> > > - WARN(1, "Memory chunk not managed or managed by a different device.");
> > > - return NULL;
> > > + replace_dr(dev, &old_dr->node, &new_dr->node);
> > > }
> > >
> > > - replace_dr(dev, &old_dr->node, &new_dr->node);
> > > -
> > > - spin_unlock_irqrestore(&dev->devres_lock, flags);
> > > -
> > > /*
> > > * We can copy the memory contents after releasing the lock as we're
> > > * no longer modifying the list links.
