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    Subject[PATCH AUTOSEL 5.5 522/542] netdevsim: disable devlink reload when resources are being used
    Date
    From: Taehee Yoo <ap420073@gmail.com>

    [ Upstream commit 6ab63366e1ec4ec1900f253aa64727b4b5f4ee73 ]

    devlink reload destroys resources and allocates resources again.
    So, when devices and ports resources are being used, devlink reload
    function should not be executed. In order to avoid this race, a new
    lock is added and new_port() and del_port() call devlink_reload_disable()
    and devlink_reload_enable().

    Thread0 Thread1
    {new/del}_port() {new/del}_port()
    devlink_reload_disable()
    devlink_reload_disable()
    devlink_reload_enable()
    //here
    devlink_reload_enable()

    Before Thread1's devlink_reload_enable(), the devlink is already allowed
    to execute reload because Thread0 allows it. devlink reload disable/enable
    variable type is bool. So the above case would exist.
    So, disable/enable should be executed atomically.
    In order to do that, a new lock is used.

    Test commands:
    modprobe netdevsim
    echo 1 > /sys/bus/netdevsim/new_device
    while :
    do
    echo 1 > /sys/devices/netdevsim1/new_port &
    echo 1 > /sys/devices/netdevsim1/del_port &
    devlink dev reload netdevsim/netdevsim1 &
    done

    Splat looks like:
    [ 23.342145][ T932] DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock))
    [ 23.342159][ T932] WARNING: CPU: 0 PID: 932 at kernel/locking/mutex-debug.c:103 mutex_destroy+0xc7/0xf0
    [ 23.344182][ T932] Modules linked in: netdevsim openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 nf_dx
    [ 23.346485][ T932] CPU: 0 PID: 932 Comm: devlink Not tainted 5.5.0+ #322
    [ 23.347696][ T932] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
    [ 23.348893][ T932] RIP: 0010:mutex_destroy+0xc7/0xf0
    [ 23.349505][ T932] Code: e0 07 83 c0 03 38 d0 7c 04 84 d2 75 2e 8b 05 00 ac b0 02 85 c0 75 8b 48 c7 c6 00 5e 07 96 40
    [ 23.351887][ T932] RSP: 0018:ffff88806208f810 EFLAGS: 00010286
    [ 23.353963][ T932] RAX: dffffc0000000008 RBX: ffff888067f6f2c0 RCX: ffffffff942c4bd4
    [ 23.355222][ T932] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff96dac5b4
    [ 23.356169][ T932] RBP: ffff888067f6f000 R08: fffffbfff2d235a5 R09: fffffbfff2d235a5
    [ 23.357160][ T932] R10: 0000000000000001 R11: fffffbfff2d235a4 R12: ffff888067f6f208
    [ 23.358288][ T932] R13: ffff88806208fa70 R14: ffff888067f6f000 R15: ffff888069ce3800
    [ 23.359307][ T932] FS: 00007fe2a3876740(0000) GS:ffff88806c000000(0000) knlGS:0000000000000000
    [ 23.360473][ T932] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    [ 23.361319][ T932] CR2: 00005561357aa000 CR3: 000000005227a006 CR4: 00000000000606f0
    [ 23.362323][ T932] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    [ 23.363417][ T932] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    [ 23.364414][ T932] Call Trace:
    [ 23.364828][ T932] nsim_dev_reload_destroy+0x77/0xb0 [netdevsim]
    [ 23.365655][ T932] nsim_dev_reload_down+0x84/0xb0 [netdevsim]
    [ 23.366433][ T932] devlink_reload+0xb1/0x350
    [ 23.367010][ T932] genl_rcv_msg+0x580/0xe90

    [ ...]

    [ 23.531729][ T1305] kernel BUG at lib/list_debug.c:53!
    [ 23.532523][ T1305] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
    [ 23.533467][ T1305] CPU: 2 PID: 1305 Comm: bash Tainted: G W 5.5.0+ #322
    [ 23.534962][ T1305] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
    [ 23.536503][ T1305] RIP: 0010:__list_del_entry_valid+0xe6/0x150
    [ 23.538346][ T1305] Code: 89 ea 48 c7 c7 00 73 1e 96 e8 df f7 4c ff 0f 0b 48 c7 c7 60 73 1e 96 e8 d1 f7 4c ff 0f 0b 44
    [ 23.541068][ T1305] RSP: 0018:ffff888047c27b58 EFLAGS: 00010282
    [ 23.542001][ T1305] RAX: 0000000000000054 RBX: ffff888067f6f318 RCX: 0000000000000000
    [ 23.543051][ T1305] RDX: 0000000000000054 RSI: 0000000000000008 RDI: ffffed1008f84f61
    [ 23.544072][ T1305] RBP: ffff88804aa0fca0 R08: ffffed100d940539 R09: ffffed100d940539
    [ 23.545085][ T1305] R10: 0000000000000001 R11: ffffed100d940538 R12: ffff888047c27cb0
    [ 23.546422][ T1305] R13: ffff88806208b840 R14: ffffffff981976c0 R15: ffff888067f6f2c0
    [ 23.547406][ T1305] FS: 00007f76c0431740(0000) GS:ffff88806c800000(0000) knlGS:0000000000000000
    [ 23.548527][ T1305] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    [ 23.549389][ T1305] CR2: 00007f5048f1a2f8 CR3: 000000004b310006 CR4: 00000000000606e0
    [ 23.550636][ T1305] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    [ 23.551578][ T1305] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    [ 23.552597][ T1305] Call Trace:
    [ 23.553004][ T1305] mutex_remove_waiter+0x101/0x520
    [ 23.553646][ T1305] __mutex_lock+0xac7/0x14b0
    [ 23.554218][ T1305] ? nsim_dev_port_del+0x4e/0x140 [netdevsim]
    [ 23.554908][ T1305] ? mutex_lock_io_nested+0x1380/0x1380
    [ 23.555570][ T1305] ? _parse_integer+0xf0/0xf0
    [ 23.556043][ T1305] ? kstrtouint+0x86/0x110
    [ 23.556504][ T1305] ? nsim_dev_port_del+0x4e/0x140 [netdevsim]
    [ 23.557133][ T1305] nsim_dev_port_del+0x4e/0x140 [netdevsim]
    [ 23.558024][ T1305] del_port_store+0xcc/0xf0 [netdevsim]
    [ ... ]

    Fixes: 75ba029f3c07 ("netdevsim: implement proper devlink reload")
    Signed-off-by: Taehee Yoo <ap420073@gmail.com>
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/netdevsim/bus.c | 19 +++++++++++++++++++
    drivers/net/netdevsim/netdevsim.h | 2 ++
    2 files changed, 21 insertions(+)

    diff --git a/drivers/net/netdevsim/bus.c b/drivers/net/netdevsim/bus.c
    index c086d1e522dc0..e455dd1cf4d0a 100644
    --- a/drivers/net/netdevsim/bus.c
    +++ b/drivers/net/netdevsim/bus.c
    @@ -97,6 +97,8 @@ new_port_store(struct device *dev, struct device_attribute *attr,
    const char *buf, size_t count)
    {
    struct nsim_bus_dev *nsim_bus_dev = to_nsim_bus_dev(dev);
    + struct nsim_dev *nsim_dev = dev_get_drvdata(dev);
    + struct devlink *devlink;
    unsigned int port_index;
    int ret;

    @@ -106,7 +108,14 @@ new_port_store(struct device *dev, struct device_attribute *attr,
    ret = kstrtouint(buf, 0, &port_index);
    if (ret)
    return ret;
    +
    + devlink = priv_to_devlink(nsim_dev);
    +
    + mutex_lock(&nsim_bus_dev->nsim_bus_reload_lock);
    + devlink_reload_disable(devlink);
    ret = nsim_dev_port_add(nsim_bus_dev, port_index);
    + devlink_reload_enable(devlink);
    + mutex_unlock(&nsim_bus_dev->nsim_bus_reload_lock);
    return ret ? ret : count;
    }

    @@ -117,6 +126,8 @@ del_port_store(struct device *dev, struct device_attribute *attr,
    const char *buf, size_t count)
    {
    struct nsim_bus_dev *nsim_bus_dev = to_nsim_bus_dev(dev);
    + struct nsim_dev *nsim_dev = dev_get_drvdata(dev);
    + struct devlink *devlink;
    unsigned int port_index;
    int ret;

    @@ -126,7 +137,14 @@ del_port_store(struct device *dev, struct device_attribute *attr,
    ret = kstrtouint(buf, 0, &port_index);
    if (ret)
    return ret;
    +
    + devlink = priv_to_devlink(nsim_dev);
    +
    + mutex_lock(&nsim_bus_dev->nsim_bus_reload_lock);
    + devlink_reload_disable(devlink);
    ret = nsim_dev_port_del(nsim_bus_dev, port_index);
    + devlink_reload_enable(devlink);
    + mutex_unlock(&nsim_bus_dev->nsim_bus_reload_lock);
    return ret ? ret : count;
    }

    @@ -311,6 +329,7 @@ nsim_bus_dev_new(unsigned int id, unsigned int port_count)
    nsim_bus_dev->dev.type = &nsim_bus_dev_type;
    nsim_bus_dev->port_count = port_count;
    nsim_bus_dev->initial_net = current->nsproxy->net_ns;
    + mutex_init(&nsim_bus_dev->nsim_bus_reload_lock);
    /* Disallow using nsim_bus_dev */
    smp_store_release(&nsim_bus_dev->init, false);

    diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h
    index ea3931391ce21..be100b11a0550 100644
    --- a/drivers/net/netdevsim/netdevsim.h
    +++ b/drivers/net/netdevsim/netdevsim.h
    @@ -240,6 +240,8 @@ struct nsim_bus_dev {
    */
    unsigned int num_vfs;
    struct nsim_vf_config *vfconfigs;
    + /* Lock for devlink->reload_enabled in netdevsim module */
    + struct mutex nsim_bus_reload_lock;
    bool init;
    };

    --
    2.20.1
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