From 2638a32348bbb1c384dbbd515fd2b12c155f0188 Mon Sep 17 00:00:00 2001 From: Dakshaja Uppalapati Date: Thu, 5 Aug 2021 18:13:32 +0530 Subject: [PATCH] RDMA/iw_cxgb4: Fix refcount underflow while destroying cqs. Previous atomic increment/decrement logic expects the atomic count to be '0' after the final decrement. Replacing atomic count with refcount does not allow that, as refcount_dec() considers count of 1 as underflow and triggers a kernel splat. Fix the current refcount logic by using the usual pattern of decrementing the refcount and test if it is '0' on the final deref in c4iw_destroy_cq(). Use wait_for_completion() instead of wait_event(). Fixes: 7183451f846d ("RDMA/cxgb4: Use refcount_t instead of atomic_t for reference counting") Link: https://lore.kernel.org/r/1628167412-12114-1-git-send-email-dakshaja@chelsio.com Signed-off-by: Dakshaja Uppalapati Reviewed-by: Potnuri Bharat Teja Signed-off-by: Jason Gunthorpe --- drivers/infiniband/hw/cxgb4/cq.c | 12 +++++++++--- drivers/infiniband/hw/cxgb4/ev.c | 6 ++---- drivers/infiniband/hw/cxgb4/iw_cxgb4.h | 3 ++- 3 files changed, 13 insertions(+), 8 deletions(-) diff --git a/drivers/infiniband/hw/cxgb4/cq.c b/drivers/infiniband/hw/cxgb4/cq.c index 6c8c910f4e86d..c7e8d7b3baa18 100644 --- a/drivers/infiniband/hw/cxgb4/cq.c +++ b/drivers/infiniband/hw/cxgb4/cq.c @@ -967,6 +967,12 @@ int c4iw_poll_cq(struct ib_cq *ibcq, int num_entries, struct ib_wc *wc) return !err || err == -ENODATA ? npolled : err; } +void c4iw_cq_rem_ref(struct c4iw_cq *chp) +{ + if (refcount_dec_and_test(&chp->refcnt)) + complete(&chp->cq_rel_comp); +} + int c4iw_destroy_cq(struct ib_cq *ib_cq, struct ib_udata *udata) { struct c4iw_cq *chp; @@ -976,8 +982,8 @@ int c4iw_destroy_cq(struct ib_cq *ib_cq, struct ib_udata *udata) chp = to_c4iw_cq(ib_cq); xa_erase_irq(&chp->rhp->cqs, chp->cq.cqid); - refcount_dec(&chp->refcnt); - wait_event(chp->wait, !refcount_read(&chp->refcnt)); + c4iw_cq_rem_ref(chp); + wait_for_completion(&chp->cq_rel_comp); ucontext = rdma_udata_to_drv_context(udata, struct c4iw_ucontext, ibucontext); @@ -1081,7 +1087,7 @@ int c4iw_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr, spin_lock_init(&chp->lock); spin_lock_init(&chp->comp_handler_lock); refcount_set(&chp->refcnt, 1); - init_waitqueue_head(&chp->wait); + init_completion(&chp->cq_rel_comp); ret = xa_insert_irq(&rhp->cqs, chp->cq.cqid, chp, GFP_KERNEL); if (ret) goto err_destroy_cq; diff --git a/drivers/infiniband/hw/cxgb4/ev.c b/drivers/infiniband/hw/cxgb4/ev.c index 7798d090888bb..34211a533d5cd 100644 --- a/drivers/infiniband/hw/cxgb4/ev.c +++ b/drivers/infiniband/hw/cxgb4/ev.c @@ -213,8 +213,7 @@ void c4iw_ev_dispatch(struct c4iw_dev *dev, struct t4_cqe *err_cqe) break; } done: - if (refcount_dec_and_test(&chp->refcnt)) - wake_up(&chp->wait); + c4iw_cq_rem_ref(chp); c4iw_qp_rem_ref(&qhp->ibqp); out: return; @@ -234,8 +233,7 @@ int c4iw_ev_handler(struct c4iw_dev *dev, u32 qid) spin_lock_irqsave(&chp->comp_handler_lock, flag); (*chp->ibcq.comp_handler)(&chp->ibcq, chp->ibcq.cq_context); spin_unlock_irqrestore(&chp->comp_handler_lock, flag); - if (refcount_dec_and_test(&chp->refcnt)) - wake_up(&chp->wait); + c4iw_cq_rem_ref(chp); } else { pr_debug("unknown cqid 0x%x\n", qid); xa_unlock_irqrestore(&dev->cqs, flag); diff --git a/drivers/infiniband/hw/cxgb4/iw_cxgb4.h b/drivers/infiniband/hw/cxgb4/iw_cxgb4.h index 3883af3d2312d..ac5f581aff4ca 100644 --- a/drivers/infiniband/hw/cxgb4/iw_cxgb4.h +++ b/drivers/infiniband/hw/cxgb4/iw_cxgb4.h @@ -428,7 +428,7 @@ struct c4iw_cq { spinlock_t lock; spinlock_t comp_handler_lock; refcount_t refcnt; - wait_queue_head_t wait; + struct completion cq_rel_comp; struct c4iw_wr_wait *wr_waitp; }; @@ -979,6 +979,7 @@ struct ib_mr *c4iw_reg_user_mr(struct ib_pd *pd, u64 start, struct ib_mr *c4iw_get_dma_mr(struct ib_pd *pd, int acc); int c4iw_dereg_mr(struct ib_mr *ib_mr, struct ib_udata *udata); int c4iw_destroy_cq(struct ib_cq *ib_cq, struct ib_udata *udata); +void c4iw_cq_rem_ref(struct c4iw_cq *chp); int c4iw_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr, struct ib_udata *udata); int c4iw_arm_cq(struct ib_cq *ibcq, enum ib_cq_notify_flags flags); -- 2.39.5