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zfcp_erp_adapter_reopen() schedules blocking of all of the adapter's rports via zfcp_scsi_schedule_rports_block() and enqueues a reopen adapter ERP action via zfcp_erp_action_enqueue(). Both are separately processed asynchronously and concurrently. Blocking of rports is done in a kworker by zfcp_scsi_rport_work(). It calls zfcp_scsi_rport_block(), which then traces a DBF REC "scpdely" via zfcp_dbf_rec_trig(). zfcp_dbf_rec_trig() acquires the DBF REC spin lock and then iterates with list_for_each() over the adapter's ERP ready list without holding the ERP lock. This opens a race window in which the current list entry can be moved to another list, causing list_for_each() to iterate forever on the wrong list, as the erp_ready_head is never encountered as terminal condition. Meanwhile the ERP action can be processed in the ERP thread by zfcp_erp_thread(). It calls zfcp_erp_strategy(), which acquires the ERP lock and then calls zfcp_erp_action_to_running() to move the ERP action from the ready to the running list. zfcp_erp_action_to_running() can move the ERP action using list_move() just during the aforementioned race window. It then traces a REC RUN "erator1" via zfcp_dbf_rec_run(). zfcp_dbf_rec_run() tries to acquire the DBF REC spin lock. If this is held by the infinitely looping kworker, it effectively spins forever. Example Sequence Diagram: Process ERP Thread rport_work ------------------- ------------------- ------------------- zfcp_erp_adapter_reopen() zfcp_erp_adapter_block() zfcp_scsi_schedule_rports_block() lock ERP zfcp_scsi_rport_work() zfcp_erp_action_enqueue(ZFCP_ERP_ACTION_REOPEN_ADAPTER) list_add_tail() on ready !(rport_task==RPORT_ADD) wake_up() ERP thread zfcp_scsi_rport_block() zfcp_dbf_rec_trig() zfcp_erp_strategy() zfcp_dbf_rec_trig() unlock ERP lock DBF REC zfcp_erp_wait() lock ERP | zfcp_erp_action_to_running() | list_for_each() ready | list_move() current entry | ready to running | zfcp_dbf_rec_run() endless loop over running | zfcp_dbf_rec_run_lvl() | lock DBF REC spins forever Any adapter recovery can trigger this, such as setting the device offline or reboot. V4.9 commit |
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| .. | ||
| Makefile | ||
| zfcp_aux.c | ||
| zfcp_ccw.c | ||
| zfcp_dbf.c | ||
| zfcp_dbf.h | ||
| zfcp_def.h | ||
| zfcp_erp.c | ||
| zfcp_ext.h | ||
| zfcp_fc.c | ||
| zfcp_fc.h | ||
| zfcp_fsf.c | ||
| zfcp_fsf.h | ||
| zfcp_qdio.c | ||
| zfcp_qdio.h | ||
| zfcp_reqlist.h | ||
| zfcp_scsi.c | ||
| zfcp_sysfs.c | ||
| zfcp_unit.c | ||