6.7-stable review patch. If anyone has any objections, please let me know.
------------------
From: Saravana Kannan saravanak@google.com
[ Upstream commit 6442d79d880cf7a2fff18779265d657fef0cce4c ]
fw_devlink can detect most overlapping/intersecting cycles. However it was missing a few corner cases because of an incorrect optimization logic that tries to avoid repeating cycle detection for devices that are already marked as part of a cycle.
Here's an example provided by Xu Yang (edited for clarity):
usb +-----+ tcpc | | +-----+ | +--| | |----------->|EP| |--+ | | +--| |EP|<-----------| | |--+ | | B | | | +-----+ | A | | +-----+ | ^ +-----+ | | | | | +-----| C |<--+ | | +-----+ usb-phy
Node A (tcpc) will be populated as device 1-0050. Node B (usb) will be populated as device 38100000.usb. Node C (usb-phy) will be populated as device 381f0040.usb-phy.
The description below uses the notation: consumer --> supplier child ==> parent
1. Node C is populated as device C. No cycles detected because cycle detection is only run when a fwnode link is converted to a device link.
2. Node B is populated as device B. As we convert B --> C into a device link we run cycle detection and find and mark the device link/fwnode link cycle: C--> A --> B.EP ==> B --> C
3. Node A is populated as device A. As we convert C --> A into a device link, we see it's already part of a cycle (from step 2) and don't run cycle detection. Thus we miss detecting the cycle: A --> B.EP ==> B --> A.EP ==> A
Looking at it another way, A depends on B in one way: A --> B.EP ==> B
But B depends on A in two ways and we only detect the first: B --> C --> A B --> A.EP ==> A
To detect both of these, we remove the incorrect optimization attempt in step 3 and run cycle detection even if the fwnode link from which the device link is being created has already been marked as part of a cycle.
Reported-by: Xu Yang xu.yang_2@nxp.com Closes: https://lore.kernel.org/lkml/DU2PR04MB8822693748725F85DC0CB86C8C792@DU2PR04M... Fixes: 3fb16866b51d ("driver core: fw_devlink: Make cycle detection more robust") Signed-off-by: Saravana Kannan saravanak@google.com Tested-by: Xu Yang xu.yang_2@nxp.com Link: https://lore.kernel.org/r/20240202095636.868578-3-saravanak@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/base/core.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c index c18c7d4c6971..f9fb69249110 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -2060,9 +2060,14 @@ static int fw_devlink_create_devlink(struct device *con,
/* * SYNC_STATE_ONLY device links don't block probing and supports cycles. - * So cycle detection isn't necessary and shouldn't be done. + * So, one might expect that cycle detection isn't necessary for them. + * However, if the device link was marked as SYNC_STATE_ONLY because + * it's part of a cycle, then we still need to do cycle detection. This + * is because the consumer and supplier might be part of multiple cycles + * and we need to detect all those cycles. */ - if (!(flags & DL_FLAG_SYNC_STATE_ONLY)) { + if (!device_link_flag_is_sync_state_only(flags) || + flags & DL_FLAG_CYCLE) { device_links_write_lock(); if (__fw_devlink_relax_cycles(con, sup_handle)) { __fwnode_link_cycle(link);