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Re: [XEN][RFC PATCH v4 11/16] common/device_tree: Add rwlock for dt_host
- To: Julien Grall <julien@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: Vikram Garhwal <vikram.garhwal@xxxxxxx>
- Date: Wed, 1 Feb 2023 09:05:24 -0800
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- Delivery-date: Wed, 01 Feb 2023 17:05:42 +0000
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Hi Julien,
On 12/7/22 8:31 AM, Julien Grall wrote:
Hi Vikram,
On 07/12/2022 06:18, Vikram Garhwal wrote:
Dynamic programming ops will modify the dt_host and there might be
other
function which are browsing the dt_host at the same time. To avoid
the race
conditions, adding rwlock for browsing the dt_host.
Looking at the user below, it is not entirely clear what the lock is
actually protecting. For instance...
Purpose of the lock was to protect the read/scanning of dt_host while we
remove the add/nodes. This lock is also used when nodes are
added/removed in "[XEN][RFC PATCH v4 12/16]: static int
remove_nodes(const struct overlay_track *tracker)".
Signed-off-by: Vikram Garhwal <vikram.garhwal@xxxxxxx>
---
xen/common/device_tree.c | 27 +++++++++++++++++++++++++++
xen/include/xen/device_tree.h | 6 ++++++
2 files changed, 33 insertions(+)
diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index acf26a411d..51ee2a5edf 100644
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -140,6 +140,8 @@ const struct dt_property *dt_find_property(const
struct dt_device_node *np,
if ( !np )
return NULL;
+ read_lock(&dt_host->lock);
+
for ( pp = np->properties; pp; pp = pp->next )
{
if ( dt_prop_cmp(pp->name, name) == 0 )
@@ -150,6 +152,7 @@ const struct dt_property *dt_find_property(const
struct dt_device_node *np,
}
}
+ read_unlock(&dt_host->lock);
return pp;
}
@@ -336,11 +339,14 @@ struct dt_device_node
*dt_find_node_by_name(struct dt_device_node *from,
struct dt_device_node *np;
struct dt_device_node *dt;
+ read_lock(&dt_host->lock);
+
dt = from ? from->allnext : dt_host;
dt_for_each_device_node(dt, np)
if ( np->name && (dt_node_cmp(np->name, name) == 0) )
break;
+ read_unlock(&dt_host->lock);
return np;
... I was expecting the read lock to also protect the value returned
from being freed. But this is not the case.
Okay. Shall I remove the lock from here and perhaps add it when
dt_find_node_by_name() and other related functions are called?
Cheers,
|
