On Thu, Aug 24, 2017 at 2:34 AM, James Smart <jsmart2...@gmail.com> wrote: > Arnd Bergmann, testing gcc-8, encountered the following: > >> This is an interesting regression with gcc-8, showing a harmless >> warning for correct code: >> >>In file included from include/linux/kernel.h:13:0, >> ... >> from drivers/scsi/lpfc/lpfc_debugfs.c:23: >> include/linux/printk.h:301:2: error: 'eq' may be used >> uninitialized in this function [-Werror=maybe-uninitialized] >> printk(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__) >> ^~~~~~ >> In file included from drivers/scsi/lpfc/lpfc_debugfs.c:58:0: >> drivers/scsi/lpfc/lpfc_debugfs.h:451:31: note: 'eq' was >> declared here > > The code is fine: a for loop which if there's at least 1 itteration, > will assign eq a value. Followed by an if test that checks for no > itterations and assigns eq a default value. But the checker doesn't > see the relationship between the two so assumes eq may not a have a > value. > > I believe, simply initializing with a NULL will solve the issue. > > Signed-off-by: James Smart <james.sm...@broadcom.com>
That's probably good enough here, as the warning is rather obscure (only one instance in the entire kernel in 1000 randconfig builds), with an unreleased compiler. Anyway, I have successfully reduced a test case and reported a gcc bug for it, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81958 The compiler test case is __attribute__ ((__cold__)) int printk(); struct lpfc_queue { int queue_id; struct lpfc_queue *hba_eq; } *cq_phba; void lpfc_debug_dump_all_queues(unsigned maxidx) { struct lpfc_queue *eq; unsigned eqidx; printk(); for (eqidx = 0; eqidx < maxidx; eqidx++) { eq = &cq_phba->hba_eq[eqidx]; if (eq->queue_id) break; } if (eqidx == maxidx) eq = &cq_phba->hba_eq[0]; printk(eq); } and I see no reason why the compiler should get this wrong. I have also come up with a different workaround of my own (sorry for the broken formatting here) and tested it successfully over night. I have definitely spent more time on it than it was worth now. Let me know if you prefer that version over yours, then I'll submit that as a proper patch with your Ack. Signed-off-by: Arnd Bergmann <a...@arndb.de> --- a/drivers/scsi/lpfc/lpfc_debugfs.h +++ b/drivers/scsi/lpfc/lpfc_debugfs.h @@ -450,7 +450,7 @@ lpfc_debug_dump_cq(struct lpfc_hba *phba, int qtype, int wqidx) { struct lpfc_queue *wq, *cq, *eq; char *qtypestr; - unsigned int eqidx; + int eqidx; /* fcp/nvme wq and cq are 1:1, thus same indexes */ @@ -478,16 +478,16 @@ lpfc_debug_dump_cq(struct lpfc_hba *phba, int qtype, int wqidx) return; for (eqidx = 0; eqidx < phba->io_channel_irqs; eqidx++) { - eq = phba->sli4_hba.hba_eq[eqidx]; - if (cq->assoc_qid == eq->queue_id) + if (cq->assoc_qid == phba->sli4_hba.hba_eq[eqidx]->queue_id) break; } if (eqidx == phba->io_channel_irqs) { pr_err("Couldn't find EQ for CQ. Using EQ[0]\n"); eqidx = 0; - eq = phba->sli4_hba.hba_eq[0]; } + eq = phba->sli4_hba.hba_eq[eqidx]; + if (qtype == DUMP_FCP || qtype == DUMP_NVME) pr_err("%s CQ: WQ[Idx:%d|Qid%d]->CQ[Idx%d|Qid%d]" "->EQ[Idx:%d|Qid:%d]:\n", Arnd
