The rtnl_lock is primarily used to serialize networking driver changes as well as to ensure that a networking driver is not removed when making changes to it. fcoe also uses the rtnl_lock to protect the fcoe hostlist. fcoe_create holds the rtnl_lock over the entirity of the routine including a the call to fcoe_ctlr_link_up. This causes the below deadlock because fcoe_ctlr_link_up acquires the fcoe_ctlr ctlr_mutex and this deadlocks with a libfcoe thread that acquires the fcoe_ctlr ctlr_mutex and then the rtnl_lock (to update a MAC address). This patch drops the rtnl_lock before calling fcoe_ctlr_link_up and therefore the deadlock is prevented. https://bugzilla.kernel.org/show_bug.cgi?id=42918 the existing dependency chain (in reverse order) is: -> #1 (&fip->ctlr_mutex){+.+...}: [<c1091f70>] lock_acquire+0x80/0x1b0 [<c147655d>] mutex_lock_nested+0x6d/0x340 [<f8970c32>] fcoe_ctlr_link_up+0x22/0x180 [libfcoe] [<f894620e>] fcoe_create+0x47e/0x6e0 [fcoe] [<f8973dd3>] fcoe_transport_create+0x143/0x250 [libfcoe] [<c10527e0>] param_attr_store+0x30/0x60 [<c1052696>] module_attr_store+0x26/0x40 [<c11a201e>] sysfs_write_file+0xae/0x100 [<c11449df>] vfs_write+0x8f/0x160 [<c1144cbd>] sys_write+0x3d/0x70 [<c147a0c4>] syscall_call+0x7/0xb -> #0 (rtnl_mutex){+.+.+.}: [<c109164b>] __lock_acquire+0x140b/0x1720 [<c1091f70>] lock_acquire+0x80/0x1b0 [<c147655d>] mutex_lock_nested+0x6d/0x340 [<c13a10c4>] rtnl_lock+0x14/0x20 [<f89445ac>] fcoe_update_src_mac+0x2c/0xb0 [fcoe] [<f8971712>] fcoe_ctlr_timer_work+0x712/0xb60 [libfcoe] [<c104fb69>] process_one_work+0x179/0x5d0 [<c10502f1>] worker_thread+0x121/0x2d0 [<c10550ed>] kthread+0x7d/0x90 [<c1481a82>] kernel_thread_helper+0x6/0x10 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&fip->ctlr_mutex); lock(rtnl_mutex); lock(&fip->ctlr_mutex); lock(rtnl_mutex); *** DEADLOCK *** Signed-off-by: Robert Love <robert.w.love@xxxxxxxxx> --- drivers/scsi/fcoe/fcoe.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-) diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c index e959960..408ca0e 100644 --- a/drivers/scsi/fcoe/fcoe.c +++ b/drivers/scsi/fcoe/fcoe.c @@ -2133,8 +2133,12 @@ static int fcoe_create(struct net_device *netdev, enum fip_state fip_mode) /* start FIP Discovery and FLOGI */ lport->boot_time = jiffies; fc_fabric_login(lport); - if (!fcoe_link_ok(lport)) + if (!fcoe_link_ok(lport)) { + rtnl_unlock(); fcoe_ctlr_link_up(&fcoe->ctlr); + mutex_unlock(&fcoe_config_mutex); + return rc; + } out_nodev: rtnl_unlock(); -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
