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3e31a490e0
Before calling ipoib_stop, rtnl_lock should be taken, then
the flow clears the IPOIB_FLAG_ADMIN_UP and IPOIB_FLAG_OPER_UP
flags, and waits for mcast completion if IPOIB_MCAST_FLAG_BUSY
is set.
On the other hand, the flow of multicast join task initializes
a mcast completion, sets the IPOIB_MCAST_FLAG_BUSY and calls
ipoib_mcast_join. If IPOIB_FLAG_OPER_UP flag is not set, this
call returns EINVAL without setting the mcast completion and
leads to a deadlock.
ipoib_stop |
| |
clear_bit(IPOIB_FLAG_ADMIN_UP) |
| |
Context Switch |
| ipoib_mcast_join_task
| |
| spin_lock_irq(lock)
| |
| init_completion(mcast)
| |
| set_bit(IPOIB_MCAST_FLAG_BUSY)
| |
| Context Switch
| |
clear_bit(IPOIB_FLAG_OPER_UP) |
| |
spin_lock_irqsave(lock) |
| |
Context Switch |
| ipoib_mcast_join
| return (-EINVAL)
| |
| spin_unlock_irq(lock)
| |
| Context Switch
| |
ipoib_mcast_dev_flush |
wait_for_completion(mcast) |
ipoib_stop will wait for mcast completion for ever, and will
not release the rtnl_lock. As a result panic occurs with the
following trace:
[13441.639268] Call Trace:
[13441.640150] [<ffffffff8168b579>] schedule+0x29/0x70
[13441.641038] [<ffffffff81688fc9>] schedule_timeout+0x239/0x2d0
[13441.641914] [<ffffffff810bc017>] ? complete+0x47/0x50
[13441.642765] [<ffffffff810a690d>] ? flush_workqueue_prep_pwqs+0x16d/0x200
[13441.643580] [<ffffffff8168b956>] wait_for_completion+0x116/0x170
[13441.644434] [<ffffffff810c4ec0>] ? wake_up_state+0x20/0x20
[13441.645293] [<ffffffffa05af170>] ipoib_mcast_dev_flush+0x150/0x190 [ib_ipoib]
[13441.646159] [<ffffffffa05ac967>] ipoib_ib_dev_down+0x37/0x60 [ib_ipoib]
[13441.647013] [<ffffffffa05a4805>] ipoib_stop+0x75/0x150 [ib_ipoib]
Fixes: 08bc327629 ("IB/ipoib: fix for rare multicast join race condition")
Signed-off-by: Feras Daoud <ferasda@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.