pds_core: fix deadlock between reset thread and remove

pci_reset_function() acquires device_lock before performing the reset.
pdsc_remove() is called by the PCI core with device_lock already held.
If pdsc_pci_reset_thread() is running when pdsc_remove() is called,
destroy_workqueue() will block waiting for the work to complete, while
the work is blocked waiting for device_lock - deadlock.

Use pci_try_reset_function() which uses pci_dev_trylock() internally.
This acquires both the device lock and the PCI config access lock
without blocking - if either lock is contended, it returns -EAGAIN
immediately. This avoids the deadlock while also ensuring proper
config space access serialization during the reset.

The pci_dev_get/put calls are also removed as they were unnecessary -
the driver-owned workqueue is destroyed in pdsc_remove(), guaranteeing
the work completes before remove returns. The PCI core holds its
reference to pci_dev throughout the entire unbind sequence.

Fixes: 81665adf25d2 ("pds_core: Fix pdsc_check_pci_health function to use work thread")
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Closes: https://patchwork.kernel.org/comment/27002369/
Signed-off-by: Nikhil P. Rao <nikhil.rao@amd.com>
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Link: https://patch.msgid.link/20260714180223.1642792-2-nikhil.rao@amd.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/amd/pds_core/core.c b/drivers/net/ethernet/amd/pds_core/core.c
index 38a2446571afabe14439ebd607dfe416eafbbfdf..1074a022a52fb4a1db7d62470c59c4ba4cf3b0a3 100644 (file)
--- a/drivers/net/ethernet/amd/pds_core/core.c
+++ b/drivers/net/ethernet/amd/pds_core/core.c
@@ -606,9 +606,10 @@ void pdsc_pci_reset_thread(struct work_struct *work)
        struct pdsc *pdsc = container_of(work, struct pdsc, pci_reset_work);
        struct pci_dev *pdev = pdsc->pdev;
 
-       pci_dev_get(pdev);
-       pci_reset_function(pdev);
-       pci_dev_put(pdev);
+       /* Use try variant to avoid deadlock with pdsc_remove().
+        * If lock is contended, the watchdog timer will retry.
+        */
+       pci_try_reset_function(pdev);
 }
 
 static void pdsc_check_pci_health(struct pdsc *pdsc)