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SubjectRe: [PATCH tip/core/urgent 2/2] rcu: remove INIT_RCU_HEAD, RCU_HEAD_INIT, RCU_HEAD
* Paul E. McKenney (paulmck@linux.vnet.ibm.com) wrote:
> From: Alexey Dobriyan <adobriyan@gmail.com>
>
> call_rcu() will unconditionally reinitialize RCU head anyway. New users
> of these macros constantly appear, so remove them.

Hrm. So do we have something that checks for double-use of a RCU head at
the moment ? (using call_rcu() twice on the same head without being
certain that the first callback have finished its execution).

I think that hiding rcu head initialization into call_rcu() is one more
step towards misuses that will silently corrupt rcu head lists. So I
think we should first add the double-use debugging option before we
remove the RCU head initializations.

Thanks,

Mathieu

>
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
> Documentation/DocBook/kernel-locking.tmpl | 8 --------
> arch/powerpc/mm/pgtable.c | 1 -
> block/cfq-iosched.c | 1 -
> block/genhd.c | 1 -
> drivers/staging/batman-adv/hard-interface.c | 1 -
> fs/file.c | 3 ---
> fs/fs-writeback.c | 1 -
> fs/partitions/check.c | 1 -
> include/linux/init_task.h | 1 -
> include/linux/rcupdate.h | 6 ------
> mm/backing-dev.c | 1 -
> mm/slob.c | 1 -
> security/selinux/avc.c | 1 -
> security/selinux/netnode.c | 2 --
> 14 files changed, 0 insertions(+), 29 deletions(-)
>
> diff --git a/Documentation/DocBook/kernel-locking.tmpl b/Documentation/DocBook/kernel-locking.tmpl
> index 084f6ad..e6cc574 100644
> --- a/Documentation/DocBook/kernel-locking.tmpl
> +++ b/Documentation/DocBook/kernel-locking.tmpl
> @@ -1725,14 +1725,6 @@ the amount of locking which needs to be done.
> if (++cache_num > MAX_CACHE_SIZE) {
> struct object *i, *outcast = NULL;
> list_for_each_entry(i, &amp;cache, list) {
> -@@ -85,6 +94,7 @@
> - obj-&gt;popularity = 0;
> - atomic_set(&amp;obj-&gt;refcnt, 1); /* The cache holds a reference */
> - spin_lock_init(&amp;obj-&gt;lock);
> -+ INIT_RCU_HEAD(&amp;obj-&gt;rcu);
> -
> - spin_lock_irqsave(&amp;cache_lock, flags);
> - __cache_add(obj);
> @@ -104,12 +114,11 @@
> struct object *cache_find(int id)
> {
> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
> index 99df697..82e38d1 100644
> --- a/arch/powerpc/mm/pgtable.c
> +++ b/arch/powerpc/mm/pgtable.c
> @@ -91,7 +91,6 @@ static void pte_free_rcu_callback(struct rcu_head *head)
>
> static void pte_free_submit(struct pte_freelist_batch *batch)
> {
> - INIT_RCU_HEAD(&batch->rcu);
> call_rcu(&batch->rcu, pte_free_rcu_callback);
> }
>
> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> index dee9d93..caa2100 100644
> --- a/block/cfq-iosched.c
> +++ b/block/cfq-iosched.c
> @@ -3719,7 +3719,6 @@ static void *cfq_init_queue(struct request_queue *q)
> * second, in order to have larger depth for async operations.
> */
> cfqd->last_delayed_sync = jiffies - HZ;
> - INIT_RCU_HEAD(&cfqd->rcu);
> return cfqd;
> }
>
> diff --git a/block/genhd.c b/block/genhd.c
> index d13ba76..27e85a2 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -987,7 +987,6 @@ int disk_expand_part_tbl(struct gendisk *disk, int partno)
> if (!new_ptbl)
> return -ENOMEM;
>
> - INIT_RCU_HEAD(&new_ptbl->rcu_head);
> new_ptbl->len = target;
>
> for (i = 0; i < len; i++)
> diff --git a/drivers/staging/batman-adv/hard-interface.c b/drivers/staging/batman-adv/hard-interface.c
> index befd488..96ea0e5 100644
> --- a/drivers/staging/batman-adv/hard-interface.c
> +++ b/drivers/staging/batman-adv/hard-interface.c
> @@ -301,7 +301,6 @@ int hardif_add_interface(char *dev, int if_num)
> batman_if->if_num = if_num;
> batman_if->dev = dev;
> batman_if->if_active = IF_INACTIVE;
> - INIT_RCU_HEAD(&batman_if->rcu);
>
> printk(KERN_INFO "batman-adv:Adding interface: %s\n", dev);
> avail_ifs++;
> diff --git a/fs/file.c b/fs/file.c
> index 34bb7f7..cccaead 100644
> --- a/fs/file.c
> +++ b/fs/file.c
> @@ -178,7 +178,6 @@ static struct fdtable * alloc_fdtable(unsigned int nr)
> fdt->open_fds = (fd_set *)data;
> data += nr / BITS_PER_BYTE;
> fdt->close_on_exec = (fd_set *)data;
> - INIT_RCU_HEAD(&fdt->rcu);
> fdt->next = NULL;
>
> return fdt;
> @@ -312,7 +311,6 @@ struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
> new_fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
> new_fdt->open_fds = (fd_set *)&newf->open_fds_init;
> new_fdt->fd = &newf->fd_array[0];
> - INIT_RCU_HEAD(&new_fdt->rcu);
> new_fdt->next = NULL;
>
> spin_lock(&oldf->file_lock);
> @@ -430,7 +428,6 @@ struct files_struct init_files = {
> .fd = &init_files.fd_array[0],
> .close_on_exec = (fd_set *)&init_files.close_on_exec_init,
> .open_fds = (fd_set *)&init_files.open_fds_init,
> - .rcu = RCU_HEAD_INIT,
> },
> .file_lock = __SPIN_LOCK_UNLOCKED(init_task.file_lock),
> };
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 76fc4d5..a79d6c3 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -77,7 +77,6 @@ static inline bool bdi_work_on_stack(struct bdi_work *work)
> static inline void bdi_work_init(struct bdi_work *work,
> struct wb_writeback_args *args)
> {
> - INIT_RCU_HEAD(&work->rcu_head);
> work->args = *args;
> work->state = WS_USED;
> }
> diff --git a/fs/partitions/check.c b/fs/partitions/check.c
> index e8865c1..03608a4 100644
> --- a/fs/partitions/check.c
> +++ b/fs/partitions/check.c
> @@ -455,7 +455,6 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
> }
>
> /* everything is up and running, commence */
> - INIT_RCU_HEAD(&p->rcu_head);
> rcu_assign_pointer(ptbl->part[partno], p);
>
> /* suppress uevent if the disk supresses it */
> diff --git a/include/linux/init_task.h b/include/linux/init_task.h
> index b1ed1cd..7996fc2 100644
> --- a/include/linux/init_task.h
> +++ b/include/linux/init_task.h
> @@ -49,7 +49,6 @@ extern struct group_info init_groups;
> { .first = &init_task.pids[PIDTYPE_PGID].node }, \
> { .first = &init_task.pids[PIDTYPE_SID].node }, \
> }, \
> - .rcu = RCU_HEAD_INIT, \
> .level = 0, \
> .numbers = { { \
> .nr = 0, \
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 872a98e..7dd951e 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -77,12 +77,6 @@ extern void rcu_scheduler_starting(void);
> #error "Unknown RCU implementation specified to kernel configuration"
> #endif
>
> -#define RCU_HEAD_INIT { .next = NULL, .func = NULL }
> -#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT
> -#define INIT_RCU_HEAD(ptr) do { \
> - (ptr)->next = NULL; (ptr)->func = NULL; \
> -} while (0)
> -
> #ifdef CONFIG_DEBUG_LOCK_ALLOC
>
> extern struct lockdep_map rcu_lock_map;
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index 0e8ca03..4745647 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -653,7 +653,6 @@ int bdi_init(struct backing_dev_info *bdi)
> bdi->max_ratio = 100;
> bdi->max_prop_frac = PROP_FRAC_BASE;
> spin_lock_init(&bdi->wb_lock);
> - INIT_RCU_HEAD(&bdi->rcu_head);
> INIT_LIST_HEAD(&bdi->bdi_list);
> INIT_LIST_HEAD(&bdi->wb_list);
> INIT_LIST_HEAD(&bdi->work_list);
> diff --git a/mm/slob.c b/mm/slob.c
> index 837ebd6..6de238d 100644
> --- a/mm/slob.c
> +++ b/mm/slob.c
> @@ -647,7 +647,6 @@ void kmem_cache_free(struct kmem_cache *c, void *b)
> if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) {
> struct slob_rcu *slob_rcu;
> slob_rcu = b + (c->size - sizeof(struct slob_rcu));
> - INIT_RCU_HEAD(&slob_rcu->head);
> slob_rcu->size = c->size;
> call_rcu(&slob_rcu->head, kmem_rcu_free);
> } else {
> diff --git a/security/selinux/avc.c b/security/selinux/avc.c
> index 989fef8..bf4e3bc 100644
> --- a/security/selinux/avc.c
> +++ b/security/selinux/avc.c
> @@ -288,7 +288,6 @@ static struct avc_node *avc_alloc_node(void)
> if (!node)
> goto out;
>
> - INIT_RCU_HEAD(&node->rhead);
> INIT_HLIST_NODE(&node->list);
> avc_cache_stats_incr(allocations);
>
> diff --git a/security/selinux/netnode.c b/security/selinux/netnode.c
> index 7100072..3dae9ef 100644
> --- a/security/selinux/netnode.c
> +++ b/security/selinux/netnode.c
> @@ -182,8 +182,6 @@ static void sel_netnode_insert(struct sel_netnode *node)
> BUG();
> }
>
> - INIT_RCU_HEAD(&node->rcu);
> -
> /* we need to impose a limit on the growth of the hash table so check
> * this bucket to make sure it is within the specified bounds */
> list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
> --
> 1.7.0
>

--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com


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