diff options
| author | Thomas Gleixner | 2015-12-13 18:02:22 +0100 |
|---|---|---|
| committer | Thomas Gleixner | 2015-12-14 10:03:46 +0100 |
| commit | 425a5072dcd1bd895eea90a6b495392b6358ebd0 (patch) | |
| tree | 312ffe3eee07e6fd1ae14732b2d67273df053548 /kernel/irq | |
| parent | f0cb32207307e9d7b3ee8117078b7a37f8d0166e (diff) | |
genirq: Free irq_desc with rcu
The new VMD device driver needs to iterate over a list of
"demultiplexing" interrupts. Protecting that list with a lock is not
possible because the list is also required in code pathes which hold
irq descriptor lock. Therefor the demultiplexing interrupt handler
would create a lock inversion scenario if it calls a demux handler
with the list protection lock held.
A solution for this is to free the irq descriptor via RCU, so the
list can be walked with rcu read lock held.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Keith Busch <keith.busch@intel.com>
Diffstat (limited to 'kernel/irq')
| -rw-r--r-- | kernel/irq/irqdesc.c | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c index 239e2ae2c947..0409da0bcc33 100644 --- a/kernel/irq/irqdesc.c +++ b/kernel/irq/irqdesc.c @@ -159,6 +159,7 @@ static struct irq_desc *alloc_desc(int irq, int node, struct module *owner) raw_spin_lock_init(&desc->lock); lockdep_set_class(&desc->lock, &irq_desc_lock_class); + init_rcu_head(&desc->rcu); desc_set_defaults(irq, desc, node, owner); @@ -171,6 +172,15 @@ err_desc: return NULL; } +static void delayed_free_desc(struct rcu_head *rhp) +{ + struct irq_desc *desc = container_of(rhp, struct irq_desc, rcu); + + free_masks(desc); + free_percpu(desc->kstat_irqs); + kfree(desc); +} + static void free_desc(unsigned int irq) { struct irq_desc *desc = irq_to_desc(irq); @@ -187,9 +197,12 @@ static void free_desc(unsigned int irq) delete_irq_desc(irq); mutex_unlock(&sparse_irq_lock); - free_masks(desc); - free_percpu(desc->kstat_irqs); - kfree(desc); + /* + * We free the descriptor, masks and stat fields via RCU. That + * allows demultiplex interrupts to do rcu based management of + * the child interrupts. + */ + call_rcu(&desc->rcu, delayed_free_desc); } static int alloc_descs(unsigned int start, unsigned int cnt, int node, |