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authorSaravana Kannan <saravanak@google.com>2021-09-29 22:05:49 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2021-10-05 18:45:54 +0300
commitf729a592adb6760013c3e48622a5bf256b992452 (patch)
treeec028f371a25d826588a359405f68957e510db19 /drivers/base
parent410d591a19543f1347bc2b4b4ec3399cb548ba47 (diff)
downloadlinux-f729a592adb6760013c3e48622a5bf256b992452.tar.xz
driver core: Reject pointless SYNC_STATE_ONLY device links
SYNC_STATE_ONLY device links intentionally allow cycles because cyclic sync_state() dependencies are valid and necessary. However a SYNC_STATE_ONLY device link where the consumer and the supplier are the same device is pointless because the device link would be deleted as soon as the device probes (because it's also the consumer) and won't affect when the sync_state() callback is called. It's a waste of CPU cycles and memory to create this device link. So reject any attempts to create such a device link. Fixes: 05ef983e0d65 ("driver core: Add device link support for SYNC_STATE_ONLY flag") Cc: stable <stable@vger.kernel.org> Reported-by: Ulf Hansson <ulf.hansson@linaro.org> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> Signed-off-by: Saravana Kannan <saravanak@google.com> Link: https://lore.kernel.org/r/20210929190549.860541-1-saravanak@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/base')
-rw-r--r--drivers/base/core.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 15986cc2fe5e..249da496581a 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -687,7 +687,8 @@ struct device_link *device_link_add(struct device *consumer,
{
struct device_link *link;
- if (!consumer || !supplier || flags & ~DL_ADD_VALID_FLAGS ||
+ if (!consumer || !supplier || consumer == supplier ||
+ flags & ~DL_ADD_VALID_FLAGS ||
(flags & DL_FLAG_STATELESS && flags & DL_MANAGED_LINK_FLAGS) ||
(flags & DL_FLAG_SYNC_STATE_ONLY &&
(flags & ~DL_FLAG_INFERRED) != DL_FLAG_SYNC_STATE_ONLY) ||