It was discussed in the Linux-RDMA list for many months. You can find a list of the archived messages here:
http://www.mail-archive.com/search?q=SA+Busy&l=linux-rdma@vger.kernel.org
The most recent version of the patch is here:
http://www.mail-archive.com/linux-rdma@vger.kernel.org/msg06644.html
Basically, the spec permits an SM to reply "busy" instead of simply tossing packets on the floor, but OFED does not handle this case right now.
-----Original Message-----
From: Moni Shoua [mailto:monis at Voltaire.COM]
Sent: Wednesday, February 02, 2011 10:42 AM
To: Mike Heinz
Cc: Vlad; nirm at voltaire.com; linux-rdma at vger.kernel.org; ewg
Subject: Re: [ewg] [PATCH] IB/core: Control number of retries for SA to leave an MCG
Mike Heinz wrote:
> Wouldn't the BUSY patch I proposed last year deal with this situation?
Can you please send a link to this patch?
>
> -----Original Message-----
> From: ewg-bounces at lists.openfabrics.org [mailto:ewg-bounces at lists.openfabrics.org] On Behalf Of Moni Shoua
> Sent: Wednesday, February 02, 2011 10:10 AM
> To: Vlad
> Cc: nirm at voltaire.com; ewg
> Subject: [ewg] [PATCH] IB/core: Control number of retries for SA to leave an MCG
>
> This patch helps when SM is busy and so an MC group is left joined
> while the host bellies that it is was left.
>
> Note: the patch below is not to driver/infiniband/core but it generates
> a patch under kernel_patches/fixes.
>
> Index: ofa_kernel-1.5.3/kernel_patches/fixes/core_0290_sysfs_mcast_leave_retries.patch
> ===================================================================
> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> +++ ofa_kernel-1.5.3/kernel_patches/fixes/core_0290_sysfs_mcast_leave_retries.patch 2011-02-02 16:52:02.000000000 +0200
> @@ -0,0 +1,46 @@
> +Add a multicast leave maximum retry setting in sys/module/ib_sa/parameters/mcast_leave_retries.
> +Add a debug print when the maximum retry count is reached.
> +
> +Signed-off-by: Nir Muchtar <nirm at voltaire.com>
> +Reviewed-by: Moni Shoua <monis at voltaire.com>
> +--
> +
> +Index: ofa_kernel-1.5.2/drivers/infiniband/core/multicast.c
> +===================================================================
> +--- ofa_kernel-1.5.2.orig/drivers/infiniband/core/multicast.c 2010-08-17 12:56:06.000000000 +0300
> ++++ ofa_kernel-1.5.2/drivers/infiniband/core/multicast.c 2010-08-17 13:15:38.000000000 +0300
> +@@ -40,6 +40,12 @@
> + #include <rdma/ib_cache.h>
> + #include "sa.h"
> +
> ++static int mcast_leave_retries = 3;
> ++
> ++module_param_call(mcast_leave_retries, param_set_int, param_get_int,
> ++ &mcast_leave_retries, 0644);
> ++MODULE_PARM_DESC(mcast_leave_retries, "Number of retries for multicast leave requests before giving up");
> ++
> + static void mcast_add_one(struct ib_device *device);
> + static void mcast_remove_one(struct ib_device *device);
> +
> +@@ -520,8 +526,11 @@
> + if (status && (group->retries > 0) &&
> + !send_leave(group, group->leave_state))
> + group->retries--;
> +- else
> ++ else {
> ++ if (status && group->retries <= 0)
> ++ printk("reached max retry count. status=%d .Giving up\n", status);
> + mcast_work_handler(&group->work);
> ++ }
> + }
> +
> + static struct mcast_group *acquire_group(struct mcast_port *port,
> +@@ -544,7 +553,7 @@
> + if (!group)
> + return NULL;
> +
> +- group->retries = 3;
> ++ group->retries = mcast_leave_retries;
> + group->port = port;
> + group->rec.mgid = *mgid;
> + group->pkey_index = MCAST_INVALID_PKEY_INDEX;
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