On 3/13/2012 5:42 PM, Love, Robert W wrote: > On 03/13/2012 03:52 PM, Robert Love wrote: >> The rtnl_mutex was held to protect calls to dev_uc_add >> and dev_uc_del. Holding rtnl is not required as those >> functions make use of the netif_addr_lock* API to >> protect the MAC changing. >> >> This change fixes the following regression by removing >> the rtnl usage when fcoe_update_src_mac is called. >> >> 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 | 2 -- >> 1 files changed, 0 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c >> index e959960..85b8203 100644 >> --- a/drivers/scsi/fcoe/fcoe.c >> +++ b/drivers/scsi/fcoe/fcoe.c >> @@ -539,13 +539,11 @@ static void fcoe_update_src_mac(struct fc_lport *lport, u8 *addr) >> struct fcoe_port *port = lport_priv(lport); >> struct fcoe_interface *fcoe = port->priv; >> >> - rtnl_lock(); >> if (!is_zero_ether_addr(port->data_src_addr)) >> dev_uc_del(fcoe->netdev, port->data_src_addr); >> if (!is_zero_ether_addr(addr)) >> dev_uc_add(fcoe->netdev, addr); >> memcpy(port->data_src_addr, addr, ETH_ALEN); >> - rtnl_unlock(); >> } >> >> /** >> > This isn't going to work. We do need rtnl_lock when calling > dev_uc_add/del to ensure the driver isn't removed while making the > change. I have an alternative patch that I'll post as soon as I clean it > up a bit. > > Nacked-by: Robert Love <robert.w.love@xxxxxxxxx> So there is a case you don't have a ref cnt on the netdev here? I guess my point is if your carrying around a ptr to the struct why haven't you incremented the refcnt. I think the dev_hold() in the create path would be enough to stop the above concern. Thanks, John -- 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
