[PATCH 2/5] xen/domain: Improve pirq handling

[Andrew Cooper <andrew.cooper3@citrix.com>]

free_pirq_struct() has no external users, so shouldn't be exposed.  Making it
static necessitates moving the function as domain_destroy() uses it.

Rework pirq_get_info() to have easier-to-follow logic.  The one functional
change is to the insertion failure path; we should not be using a full
call_rcu() chain to free an otherwise local structure we failed to insert into
the radix tree to begin with.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Wei Liu <wl@xen.org>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Julien Grall <julien@xen.org>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
CC: Bertrand Marquis <bertrand.marquis@arm.com>
---
 xen/common/domain.c      | 62 ++++++++++++++++++++++++++----------------------
 xen/include/xen/domain.h |  1 -
 2 files changed, 33 insertions(+), 30 deletions(-)

diff --git a/xen/common/domain.c b/xen/common/domain.c
index 562872cdf87a..a53dd114d5ba 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -365,6 +365,39 @@ static int __init parse_extra_guest_irqs(const char *s)
 }
 custom_param("extra_guest_irqs", parse_extra_guest_irqs);
 
+static void _free_pirq_struct(struct rcu_head *head)
+{
+    xfree(container_of(head, struct pirq, rcu_head));
+}
+
+static void free_pirq_struct(void *ptr)
+{
+    struct pirq *pirq = ptr;
+
+    call_rcu(&pirq->rcu_head, _free_pirq_struct);
+}
+
+struct pirq *pirq_get_info(struct domain *d, int pirq)
+{
+    struct pirq *info = pirq_info(d, pirq);
+
+    if ( likely(info) )
+        return info;
+
+    info = alloc_pirq_struct(d);
+    if ( unlikely(!info) )
+        return NULL;
+
+    info->pirq = pirq;
+    if ( likely(radix_tree_insert(&d->pirq_tree, pirq, info) == 0) )
+        return info; /* Success. */
+
+    /* Don't use call_rcu() to free a struct we failed to insert. */
+    _free_pirq_struct(&info->rcu_head);
+
+    return NULL;
+}
+
 /*
  * Release resources held by a domain.  There may or may not be live
  * references to the domain, and it may or may not be fully constructed.
@@ -1789,35 +1822,6 @@ long do_vm_assist(unsigned int cmd, unsigned int type)
 }
 #endif
 
-struct pirq *pirq_get_info(struct domain *d, int pirq)
-{
-    struct pirq *info = pirq_info(d, pirq);
-
-    if ( !info && (info = alloc_pirq_struct(d)) != NULL )
-    {
-        info->pirq = pirq;
-        if ( radix_tree_insert(&d->pirq_tree, pirq, info) )
-        {
-            free_pirq_struct(info);
-            info = NULL;
-        }
-    }
-
-    return info;
-}
-
-static void _free_pirq_struct(struct rcu_head *head)
-{
-    xfree(container_of(head, struct pirq, rcu_head));
-}
-
-void free_pirq_struct(void *ptr)
-{
-    struct pirq *pirq = ptr;
-
-    call_rcu(&pirq->rcu_head, _free_pirq_struct);
-}
-
 struct migrate_info {
     long (*func)(void *data);
     void *data;
diff --git a/xen/include/xen/domain.h b/xen/include/xen/domain.h
index 160c8dbdab33..b4d202fda9fd 100644
--- a/xen/include/xen/domain.h
+++ b/xen/include/xen/domain.h
@@ -44,7 +44,6 @@ void free_vcpu_struct(struct vcpu *v);
 #ifndef alloc_pirq_struct
 struct pirq *alloc_pirq_struct(struct domain *);
 #endif
-void free_pirq_struct(void *);
 
 /*
  * Initialise/destroy arch-specific details of a VCPU.
-- 
2.11.0