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>>>> +        if (!rdtgrp) { >>>> +            ret = -ENOENT; >>>> +            goto out_unlock; >>> >>> If this fails there needs to be content in last_cmd_status. Otherwise this >>> fails and then last_cmd_status reads "ok" or worse .. an old failure message. >> >> if (WARN_ON(!rdtgrp)) { >>     rdt_last_cmd_puts("Invalid kernel mode group\n"); >>     ret = -ENOENT; >>     goto out_unlock; >> } > It is not clear to me why the WARN_ON() was added. Is the resource group not being > associated with kernel mode not a legitimate scenario if the kernel mode group was > re-assigned while the reader of this file was blocked on the mutex? > A valid group is required whenever any global mode is enabled. Reaching this condition without one is unexpected and should be treated as a bug. To help catch this, I added a WARN_ON() to log the issue. I think updating last_cmd_status is reasonable as well and should provide the necessary user-visible error indication. thanks Babu