ib_srp: Avoid that module removal can trigger a deadlock

Avoid that scsi_remove_host() is invoked from the context of a work
queue thread on which work has been queued that scsi_remove_host()
might be waiting for. That avoids that module removal of ib_srp
triggers a deadlock on a pre-2.6.36 kernel. This patch has been
tested on RHEL 6.1, RHEL 6.2, RHEL 6.3 and SLES 11 SP2.

Reported-by: Rupert Dance <rsdance@soft-forge.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>

diff --git a/patches/0025-ib_srp-Backport-to-older-kernels.patch b/patches/0025-ib_srp-Backport-to-older-kernels.patch
index 20edccf0d93c98d79399193230caaa95d7a43b7d..d070430b4f9b9a98322ca4dd6fa6273a9851931b 100644 (file)
--- a/patches/0025-ib_srp-Backport-to-older-kernels.patch
+++ b/patches/0025-ib_srp-Backport-to-older-kernels.patch
@@ -12,7 +12,7 @@ Signed-off-by: Bart Van Assche <bvanassche@acm.org>
  1 file changed, 108 insertions(+), 3 deletions(-)
 
 diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
-index bcbf22e..fab74e0 100644
+index bcbf22e..d42e9c4 100644
 --- a/drivers/infiniband/ulp/srp/ib_srp.c
 +++ b/drivers/infiniband/ulp/srp/ib_srp.c
 @@ -30,8 +30,13 @@
@@ -29,7 +29,7 @@ index bcbf22e..fab74e0 100644
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/slab.h>
-@@ -41,21 +46,27 @@
+@@ -41,21 +46,32 @@
  #include <linux/random.h>
  #include <linux/jiffies.h>
  
@@ -56,23 +56,16 @@ index bcbf22e..fab74e0 100644
 +#ifndef pr_warn
 +#define pr_warn pr_warning
 +#endif
++
++#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 36)
++static struct workqueue_struct *srp_wq;
++#define ib_wq srp_wq
++#endif
 +
  MODULE_AUTHOR("Roland Dreier");
  MODULE_DESCRIPTION("InfiniBand SCSI RDMA Protocol initiator "
                   "v" DRV_VERSION " (" DRV_RELDATE ")");
-@@ -675,7 +686,11 @@ err:
-       if (target->state == SRP_TARGET_CONNECTING) {
-               target->state = SRP_TARGET_DEAD;
-               INIT_WORK(&target->work, srp_remove_work);
-+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 36)
-               queue_work(ib_wq, &target->work);
-+#else
-+              schedule_work(&target->work);
-+#endif
-       }
-       spin_unlock_irq(&target->lock);
- 
-@@ -1254,7 +1269,50 @@ static void srp_send_completion(struct ib_cq *cq, void *target_ptr)
+@@ -1254,7 +1270,50 @@ static void srp_send_completion(struct ib_cq *cq, void *target_ptr)
        }
  }
  
@@ -124,7 +117,7 @@ index bcbf22e..fab74e0 100644
  {
        struct srp_target_port *target = host_to_target(shost);
        struct srp_request *req;
-@@ -1822,6 +1880,9 @@ static struct scsi_host_template srp_template = {
+@@ -1822,6 +1881,9 @@ static struct scsi_host_template srp_template = {
        .name                           = "InfiniBand SRP initiator",
        .proc_name                      = DRV_NAME,
        .info                           = srp_target_info,
@@ -134,18 +127,32 @@ index bcbf22e..fab74e0 100644
        .queuecommand                   = srp_queuecommand,
        .eh_abort_handler               = srp_abort,
        .eh_device_reset_handler        = srp_reset_device,
-@@ -2412,7 +2473,11 @@ static void srp_remove_one(struct ib_device *device)
-                * started before we marked our target ports as
-                * removed, and any target port removal tasks.
-                */
-+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 36)
-               flush_workqueue(ib_wq);
-+#else
-+              flush_scheduled_work();
+@@ -2491,11 +2553,25 @@ static int __init srp_init_module(void)
+               return ret;
+       }
+ 
++#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 36)
++      srp_wq = create_workqueue("srp");
++      if (IS_ERR(srp_wq)) {
++              ib_unregister_client(&srp_client);
++              ib_sa_unregister_client(&srp_sa_client);
++              class_unregister(&srp_class);
++              srp_release_transport(ib_srp_transport_template);
++              return PTR_ERR(srp_wq);
++      }
 +#endif
++
+       return 0;
+ }
  
-               list_for_each_entry_safe(target, tmp_target,
-                                        &host->target_list, list) {
+ static void __exit srp_cleanup_module(void)
+ {
++#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 36)
++      destroy_workqueue(srp_wq);
++#endif
+       ib_unregister_client(&srp_client);
+       ib_sa_unregister_client(&srp_sa_client);
+       class_unregister(&srp_class);
 -- 
 1.7.9.5