From: Arnd Bergmann <arnd@arndb.de>
To: Sagi Grimberg <sagi@grimberg.me>
Cc: Binoy Jayan <binoy.jayan@linaro.org>,
Doug Ledford <dledford@redhat.com>,
Sean Hefty <sean.hefty@intel.com>,
Hal Rosenstock <hal.rosenstock@gmail.com>,
Leon Romanovsky <leonro@mellanox.com>,
Sagi Grimberg <sagig@mellanox.com>,
Bart Van Assche <bart.vanassche@sandisk.com>,
Nicholas Bellinger <nab@linux-iscsi.org>,
Jenny Derzhavetz <jennyf@mellanox.com>,
Ira Weiny <ira.weiny@intel.com>,
Steve Wise <swise@opengridcomputing.com>,
Mark Bloch <markb@mellanox.com>,
Tatyana E Nikolova <tatyana.e.nikolova@intel.com>,
Matan Barak <matanb@mellanox.com>, Lijun Ou <oulijun@huawei.com>,
"Wei Hu(Xavier)" <xavier.huwei@huawei.com>,
Faisal Latif <faisal.latif@intel.com>,
Mustafa Ismail <mustafa.ismail@intel.com>,
Mark Brown <broonie@kernel.org>,
linux-rdma@vg
Subject: Re: [PATCH v5 5/9] IB/isert: Replace semaphore sem with completion
Date: Mon, 21 Nov 2016 11:22:12 +0100 [thread overview]
Message-ID: <2625189.HB0S3sfnY7@wuerfel> (raw)
In-Reply-To: <e1e4788d-9250-d4c3-937f-262bd9264a76@grimberg.me>
On Monday, November 21, 2016 9:36:22 AM CET Sagi Grimberg wrote:
> > diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
> > index 6dd43f6..de80f56 100644
> > --- a/drivers/infiniband/ulp/isert/ib_isert.c
> > +++ b/drivers/infiniband/ulp/isert/ib_isert.c
> > @@ -619,7 +619,7 @@
> > mutex_unlock(&isert_np->mutex);
> >
> > isert_info("np %p: Allow accept_np to continue\n", isert_np);
> > - up(&isert_np->sem);
> > + complete(&isert_np->comp);
> > }
> >
> > static void
> > @@ -2311,7 +2311,7 @@ struct rdma_cm_id *
> > isert_err("Unable to allocate struct isert_np\n");
> > return -ENOMEM;
> > }
> > - sema_init(&isert_np->sem, 0);
> > + init_completion(&isert_np->comp);
>
> This is still racy, a connect event can complete just before we
> init the completion and *will* get lost...
>
> This code started off with a waitqueue which exposes the same
> problem, see:
> 531b7bf4bd79 Target/iser: Fix iscsit_accept_np and rdma_cm racy flow
>
> So, still NAK from me...
I don't see what you mean here. The code using a waitqueue had no
counter but the completion does. I had suggested that Binoy add
a comment into the code about this, as it is a rarely used
property of completions, but it does seem entirely valid to me.
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: Sagi Grimberg <sagi@grimberg.me>
Cc: Binoy Jayan <binoy.jayan@linaro.org>,
Doug Ledford <dledford@redhat.com>,
Sean Hefty <sean.hefty@intel.com>,
Hal Rosenstock <hal.rosenstock@gmail.com>,
Leon Romanovsky <leonro@mellanox.com>,
Sagi Grimberg <sagig@mellanox.com>,
Bart Van Assche <bart.vanassche@sandisk.com>,
Nicholas Bellinger <nab@linux-iscsi.org>,
Jenny Derzhavetz <jennyf@mellanox.com>,
Ira Weiny <ira.weiny@intel.com>,
Steve Wise <swise@opengridcomputing.com>,
Mark Bloch <markb@mellanox.com>,
Tatyana E Nikolova <tatyana.e.nikolova@intel.com>,
Matan Barak <matanb@mellanox.com>, Lijun Ou <oulijun@huawei.com>,
"Wei Hu(Xavier)" <xavier.huwei@huawei.com>,
Faisal Latif <faisal.latif@intel.com>,
Mustafa Ismail <mustafa.ismail@intel.com>,
Mark Brown <broonie@kernel.org>,
linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org,
target-devel@vger.kernel.org
Subject: Re: [PATCH v5 5/9] IB/isert: Replace semaphore sem with completion
Date: Mon, 21 Nov 2016 11:22:12 +0100 [thread overview]
Message-ID: <2625189.HB0S3sfnY7@wuerfel> (raw)
In-Reply-To: <e1e4788d-9250-d4c3-937f-262bd9264a76@grimberg.me>
On Monday, November 21, 2016 9:36:22 AM CET Sagi Grimberg wrote:
> > diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
> > index 6dd43f6..de80f56 100644
> > --- a/drivers/infiniband/ulp/isert/ib_isert.c
> > +++ b/drivers/infiniband/ulp/isert/ib_isert.c
> > @@ -619,7 +619,7 @@
> > mutex_unlock(&isert_np->mutex);
> >
> > isert_info("np %p: Allow accept_np to continue\n", isert_np);
> > - up(&isert_np->sem);
> > + complete(&isert_np->comp);
> > }
> >
> > static void
> > @@ -2311,7 +2311,7 @@ struct rdma_cm_id *
> > isert_err("Unable to allocate struct isert_np\n");
> > return -ENOMEM;
> > }
> > - sema_init(&isert_np->sem, 0);
> > + init_completion(&isert_np->comp);
>
> This is still racy, a connect event can complete just before we
> init the completion and *will* get lost...
>
> This code started off with a waitqueue which exposes the same
> problem, see:
> 531b7bf4bd79 Target/iser: Fix iscsit_accept_np and rdma_cm racy flow
>
> So, still NAK from me...
I don't see what you mean here. The code using a waitqueue had no
counter but the completion does. I had suggested that Binoy add
a comment into the code about this, as it is a rarely used
property of completions, but it does seem entirely valid to me.
Arnd
next prev parent reply other threads:[~2016-11-21 10:22 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-21 6:08 [PATCH v5 0/9] infiniband: Remove semaphores Binoy Jayan
2016-11-21 6:08 ` Binoy Jayan
2016-11-21 6:08 ` [PATCH v5 1/9] IB/core: iwpm_nlmsg_request: Replace semaphore with completion Binoy Jayan
2016-11-21 6:08 ` [PATCH v5 2/9] IB/core: Replace semaphore sm_sem with an atomic wait Binoy Jayan
[not found] ` <CA+55aFxGjaqduhRCyk0mVxEA7aqQ-omdG8SBreZ=x5cW2ovngQ@mail.gmail.com>
2016-11-21 16:52 ` Arnd Bergmann
2016-11-21 16:52 ` Arnd Bergmann
2016-11-21 16:57 ` Christoph Hellwig
2016-11-21 16:57 ` Christoph Hellwig
2016-11-21 17:57 ` Linus Torvalds
2016-11-21 17:57 ` Linus Torvalds
2016-11-21 22:51 ` Arnd Bergmann
2016-11-21 22:51 ` Arnd Bergmann
[not found] ` <1479708496-9828-1-git-send-email-binoy.jayan-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2016-11-21 6:08 ` [PATCH v5 3/9] IB/hns: Replace semaphore poll_sem with mutex Binoy Jayan
2016-11-21 6:08 ` Binoy Jayan
2016-11-21 6:08 ` [PATCH v5 4/9] IB/mthca: " Binoy Jayan
2016-11-21 6:08 ` [PATCH v5 5/9] IB/isert: Replace semaphore sem with completion Binoy Jayan
2016-11-21 7:36 ` Sagi Grimberg
2016-11-21 10:22 ` Arnd Bergmann [this message]
2016-11-21 10:22 ` Arnd Bergmann
2016-11-21 12:33 ` Sagi Grimberg
2016-11-21 12:33 ` Sagi Grimberg
2016-11-21 14:50 ` Arnd Bergmann
2016-11-21 14:50 ` Arnd Bergmann
2016-11-21 6:08 ` [PATCH v5 6/9] IB/hns: Replace counting semaphore event_sem with wait_event Binoy Jayan
2016-11-21 6:08 ` [PATCH v5 7/9] IB/mthca: " Binoy Jayan
2016-11-21 6:08 ` [PATCH v5 8/9] IB/mlx5: Add helper mlx5_ib_post_send_wait Binoy Jayan
2016-11-21 6:08 ` [PATCH v5 9/9] IB/mlx5: Replace semaphore umr_common:sem with wait_event Binoy Jayan
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