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    Subject[PATCH 5.14 816/849] PM: sleep: Avoid calling put_device() under dpm_list_mtx
    Date
    From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

    commit 2aa36604e8243698ff22bd5fef0dd0c6bb07ba92 upstream.

    It is generally unsafe to call put_device() with dpm_list_mtx held,
    because the given device's release routine may carry out an action
    depending on that lock which then may deadlock, so modify the
    system-wide suspend and resume of devices to always drop dpm_list_mtx
    before calling put_device() (and adjust white space somewhat while
    at it).

    For instance, this prevents the following splat from showing up in
    the kernel log after a system resume in certain configurations:

    [ 3290.969514] ======================================================
    [ 3290.969517] WARNING: possible circular locking dependency detected
    [ 3290.969519] 5.15.0+ #2420 Tainted: G S
    [ 3290.969523] ------------------------------------------------------
    [ 3290.969525] systemd-sleep/4553 is trying to acquire lock:
    [ 3290.969529] ffff888117ab1138 ((wq_completion)hci0#2){+.+.}-{0:0}, at: flush_workqueue+0x87/0x4a0
    [ 3290.969554]
    but task is already holding lock:
    [ 3290.969556] ffffffff8280fca8 (dpm_list_mtx){+.+.}-{3:3}, at: dpm_resume+0x12e/0x3e0
    [ 3290.969571]
    which lock already depends on the new lock.

    [ 3290.969573]
    the existing dependency chain (in reverse order) is:
    [ 3290.969575]
    -> #3 (dpm_list_mtx){+.+.}-{3:3}:
    [ 3290.969583] __mutex_lock+0x9d/0xa30
    [ 3290.969591] device_pm_add+0x2e/0xe0
    [ 3290.969597] device_add+0x4d5/0x8f0
    [ 3290.969605] hci_conn_add_sysfs+0x43/0xb0 [bluetooth]
    [ 3290.969689] hci_conn_complete_evt.isra.71+0x124/0x750 [bluetooth]
    [ 3290.969747] hci_event_packet+0xd6c/0x28a0 [bluetooth]
    [ 3290.969798] hci_rx_work+0x213/0x640 [bluetooth]
    [ 3290.969842] process_one_work+0x2aa/0x650
    [ 3290.969851] worker_thread+0x39/0x400
    [ 3290.969859] kthread+0x142/0x170
    [ 3290.969865] ret_from_fork+0x22/0x30
    [ 3290.969872]
    -> #2 (&hdev->lock){+.+.}-{3:3}:
    [ 3290.969881] __mutex_lock+0x9d/0xa30
    [ 3290.969887] hci_event_packet+0xba/0x28a0 [bluetooth]
    [ 3290.969935] hci_rx_work+0x213/0x640 [bluetooth]
    [ 3290.969978] process_one_work+0x2aa/0x650
    [ 3290.969985] worker_thread+0x39/0x400
    [ 3290.969993] kthread+0x142/0x170
    [ 3290.969999] ret_from_fork+0x22/0x30
    [ 3290.970004]
    -> #1 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}:
    [ 3290.970013] process_one_work+0x27d/0x650
    [ 3290.970020] worker_thread+0x39/0x400
    [ 3290.970028] kthread+0x142/0x170
    [ 3290.970033] ret_from_fork+0x22/0x30
    [ 3290.970038]
    -> #0 ((wq_completion)hci0#2){+.+.}-{0:0}:
    [ 3290.970047] __lock_acquire+0x15cb/0x1b50
    [ 3290.970054] lock_acquire+0x26c/0x300
    [ 3290.970059] flush_workqueue+0xae/0x4a0
    [ 3290.970066] drain_workqueue+0xa1/0x130
    [ 3290.970073] destroy_workqueue+0x34/0x1f0
    [ 3290.970081] hci_release_dev+0x49/0x180 [bluetooth]
    [ 3290.970130] bt_host_release+0x1d/0x30 [bluetooth]
    [ 3290.970195] device_release+0x33/0x90
    [ 3290.970201] kobject_release+0x63/0x160
    [ 3290.970211] dpm_resume+0x164/0x3e0
    [ 3290.970215] dpm_resume_end+0xd/0x20
    [ 3290.970220] suspend_devices_and_enter+0x1a4/0xba0
    [ 3290.970229] pm_suspend+0x26b/0x310
    [ 3290.970236] state_store+0x42/0x90
    [ 3290.970243] kernfs_fop_write_iter+0x135/0x1b0
    [ 3290.970251] new_sync_write+0x125/0x1c0
    [ 3290.970257] vfs_write+0x360/0x3c0
    [ 3290.970263] ksys_write+0xa7/0xe0
    [ 3290.970269] do_syscall_64+0x3a/0x80
    [ 3290.970276] entry_SYSCALL_64_after_hwframe+0x44/0xae
    [ 3290.970284]
    other info that might help us debug this:

    [ 3290.970285] Chain exists of:
    (wq_completion)hci0#2 --> &hdev->lock --> dpm_list_mtx

    [ 3290.970297] Possible unsafe locking scenario:

    [ 3290.970299] CPU0 CPU1
    [ 3290.970300] ---- ----
    [ 3290.970302] lock(dpm_list_mtx);
    [ 3290.970306] lock(&hdev->lock);
    [ 3290.970310] lock(dpm_list_mtx);
    [ 3290.970314] lock((wq_completion)hci0#2);
    [ 3290.970319]
    *** DEADLOCK ***

    [ 3290.970321] 7 locks held by systemd-sleep/4553:
    [ 3290.970325] #0: ffff888103bcd448 (sb_writers#4){.+.+}-{0:0}, at: ksys_write+0xa7/0xe0
    [ 3290.970341] #1: ffff888115a14488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x103/0x1b0
    [ 3290.970355] #2: ffff888100f719e0 (kn->active#233){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x10c/0x1b0
    [ 3290.970369] #3: ffffffff82661048 (autosleep_lock){+.+.}-{3:3}, at: state_store+0x12/0x90
    [ 3290.970384] #4: ffffffff82658ac8 (system_transition_mutex){+.+.}-{3:3}, at: pm_suspend+0x9f/0x310
    [ 3290.970399] #5: ffffffff827f2a48 (acpi_scan_lock){+.+.}-{3:3}, at: acpi_suspend_begin+0x4c/0x80
    [ 3290.970416] #6: ffffffff8280fca8 (dpm_list_mtx){+.+.}-{3:3}, at: dpm_resume+0x12e/0x3e0
    [ 3290.970428]
    stack backtrace:
    [ 3290.970431] CPU: 3 PID: 4553 Comm: systemd-sleep Tainted: G S 5.15.0+ #2420
    [ 3290.970438] Hardware name: Dell Inc. XPS 13 9380/0RYJWW, BIOS 1.5.0 06/03/2019
    [ 3290.970441] Call Trace:
    [ 3290.970446] dump_stack_lvl+0x44/0x57
    [ 3290.970454] check_noncircular+0x105/0x120
    [ 3290.970468] ? __lock_acquire+0x15cb/0x1b50
    [ 3290.970474] __lock_acquire+0x15cb/0x1b50
    [ 3290.970487] lock_acquire+0x26c/0x300
    [ 3290.970493] ? flush_workqueue+0x87/0x4a0
    [ 3290.970503] ? __raw_spin_lock_init+0x3b/0x60
    [ 3290.970510] ? lockdep_init_map_type+0x58/0x240
    [ 3290.970519] flush_workqueue+0xae/0x4a0
    [ 3290.970526] ? flush_workqueue+0x87/0x4a0
    [ 3290.970544] ? drain_workqueue+0xa1/0x130
    [ 3290.970552] drain_workqueue+0xa1/0x130
    [ 3290.970561] destroy_workqueue+0x34/0x1f0
    [ 3290.970572] hci_release_dev+0x49/0x180 [bluetooth]
    [ 3290.970624] bt_host_release+0x1d/0x30 [bluetooth]
    [ 3290.970687] device_release+0x33/0x90
    [ 3290.970695] kobject_release+0x63/0x160
    [ 3290.970705] dpm_resume+0x164/0x3e0
    [ 3290.970710] ? dpm_resume_early+0x251/0x3b0
    [ 3290.970718] dpm_resume_end+0xd/0x20
    [ 3290.970723] suspend_devices_and_enter+0x1a4/0xba0
    [ 3290.970737] pm_suspend+0x26b/0x310
    [ 3290.970746] state_store+0x42/0x90
    [ 3290.970755] kernfs_fop_write_iter+0x135/0x1b0
    [ 3290.970764] new_sync_write+0x125/0x1c0
    [ 3290.970777] vfs_write+0x360/0x3c0
    [ 3290.970785] ksys_write+0xa7/0xe0
    [ 3290.970794] do_syscall_64+0x3a/0x80
    [ 3290.970803] entry_SYSCALL_64_after_hwframe+0x44/0xae
    [ 3290.970811] RIP: 0033:0x7f41b1328164
    [ 3290.970819] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00 00 8b 05 4a d2 2c 00 48 63 ff 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 f3 c3 66 90 55 53 48 89 d5 48 89 f3 48 83
    [ 3290.970824] RSP: 002b:00007ffe6ae21b28 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
    [ 3290.970831] RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007f41b1328164
    [ 3290.970836] RDX: 0000000000000004 RSI: 000055965e651070 RDI: 0000000000000004
    [ 3290.970839] RBP: 000055965e651070 R08: 000055965e64f390 R09: 00007f41b1e3d1c0
    [ 3290.970843] R10: 000000000000000a R11: 0000000000000246 R12: 0000000000000004
    [ 3290.970846] R13: 0000000000000001 R14: 000055965e64f2b0 R15: 0000000000000004

    Cc: All applicable <stable@vger.kernel.org>
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/base/power/main.c | 84 +++++++++++++++++++++++++++++++---------------
    1 file changed, 57 insertions(+), 27 deletions(-)

    --- a/drivers/base/power/main.c
    +++ b/drivers/base/power/main.c
    @@ -711,6 +711,7 @@ static void dpm_noirq_resume_devices(pm_
    dev = to_device(dpm_noirq_list.next);
    get_device(dev);
    list_move_tail(&dev->power.entry, &dpm_late_early_list);
    +
    mutex_unlock(&dpm_list_mtx);

    if (!is_async(dev)) {
    @@ -725,8 +726,9 @@ static void dpm_noirq_resume_devices(pm_
    }
    }

    - mutex_lock(&dpm_list_mtx);
    put_device(dev);
    +
    + mutex_lock(&dpm_list_mtx);
    }
    mutex_unlock(&dpm_list_mtx);
    async_synchronize_full();
    @@ -852,6 +854,7 @@ void dpm_resume_early(pm_message_t state
    dev = to_device(dpm_late_early_list.next);
    get_device(dev);
    list_move_tail(&dev->power.entry, &dpm_suspended_list);
    +
    mutex_unlock(&dpm_list_mtx);

    if (!is_async(dev)) {
    @@ -865,8 +868,10 @@ void dpm_resume_early(pm_message_t state
    pm_dev_err(dev, state, " early", error);
    }
    }
    - mutex_lock(&dpm_list_mtx);
    +
    put_device(dev);
    +
    + mutex_lock(&dpm_list_mtx);
    }
    mutex_unlock(&dpm_list_mtx);
    async_synchronize_full();
    @@ -1029,7 +1034,12 @@ void dpm_resume(pm_message_t state)
    }
    if (!list_empty(&dev->power.entry))
    list_move_tail(&dev->power.entry, &dpm_prepared_list);
    +
    + mutex_unlock(&dpm_list_mtx);
    +
    put_device(dev);
    +
    + mutex_lock(&dpm_list_mtx);
    }
    mutex_unlock(&dpm_list_mtx);
    async_synchronize_full();
    @@ -1107,14 +1117,16 @@ void dpm_complete(pm_message_t state)
    get_device(dev);
    dev->power.is_prepared = false;
    list_move(&dev->power.entry, &list);
    +
    mutex_unlock(&dpm_list_mtx);

    trace_device_pm_callback_start(dev, "", state.event);
    device_complete(dev, state);
    trace_device_pm_callback_end(dev, 0);

    - mutex_lock(&dpm_list_mtx);
    put_device(dev);
    +
    + mutex_lock(&dpm_list_mtx);
    }
    list_splice(&list, &dpm_list);
    mutex_unlock(&dpm_list_mtx);
    @@ -1299,17 +1311,21 @@ static int dpm_noirq_suspend_devices(pm_
    error = device_suspend_noirq(dev);

    mutex_lock(&dpm_list_mtx);
    +
    if (error) {
    pm_dev_err(dev, state, " noirq", error);
    dpm_save_failed_dev(dev_name(dev));
    - put_device(dev);
    - break;
    - }
    - if (!list_empty(&dev->power.entry))
    + } else if (!list_empty(&dev->power.entry)) {
    list_move(&dev->power.entry, &dpm_noirq_list);
    + }
    +
    + mutex_unlock(&dpm_list_mtx);
    +
    put_device(dev);

    - if (async_error)
    + mutex_lock(&dpm_list_mtx);
    +
    + if (error || async_error)
    break;
    }
    mutex_unlock(&dpm_list_mtx);
    @@ -1476,23 +1492,28 @@ int dpm_suspend_late(pm_message_t state)
    struct device *dev = to_device(dpm_suspended_list.prev);

    get_device(dev);
    +
    mutex_unlock(&dpm_list_mtx);

    error = device_suspend_late(dev);

    mutex_lock(&dpm_list_mtx);
    +
    if (!list_empty(&dev->power.entry))
    list_move(&dev->power.entry, &dpm_late_early_list);

    if (error) {
    pm_dev_err(dev, state, " late", error);
    dpm_save_failed_dev(dev_name(dev));
    - put_device(dev);
    - break;
    }
    +
    + mutex_unlock(&dpm_list_mtx);
    +
    put_device(dev);

    - if (async_error)
    + mutex_lock(&dpm_list_mtx);
    +
    + if (error || async_error)
    break;
    }
    mutex_unlock(&dpm_list_mtx);
    @@ -1752,21 +1773,27 @@ int dpm_suspend(pm_message_t state)
    struct device *dev = to_device(dpm_prepared_list.prev);

    get_device(dev);
    +
    mutex_unlock(&dpm_list_mtx);

    error = device_suspend(dev);

    mutex_lock(&dpm_list_mtx);
    +
    if (error) {
    pm_dev_err(dev, state, "", error);
    dpm_save_failed_dev(dev_name(dev));
    - put_device(dev);
    - break;
    - }
    - if (!list_empty(&dev->power.entry))
    + } else if (!list_empty(&dev->power.entry)) {
    list_move(&dev->power.entry, &dpm_suspended_list);
    + }
    +
    + mutex_unlock(&dpm_list_mtx);
    +
    put_device(dev);
    - if (async_error)
    +
    + mutex_lock(&dpm_list_mtx);
    +
    + if (error || async_error)
    break;
    }
    mutex_unlock(&dpm_list_mtx);
    @@ -1883,6 +1910,7 @@ int dpm_prepare(pm_message_t state)
    struct device *dev = to_device(dpm_list.next);

    get_device(dev);
    +
    mutex_unlock(&dpm_list_mtx);

    trace_device_pm_callback_start(dev, "", state.event);
    @@ -1890,21 +1918,23 @@ int dpm_prepare(pm_message_t state)
    trace_device_pm_callback_end(dev, error);

    mutex_lock(&dpm_list_mtx);
    - if (error) {
    - if (error == -EAGAIN) {
    - put_device(dev);
    - error = 0;
    - continue;
    - }
    +
    + if (!error) {
    + dev->power.is_prepared = true;
    + if (!list_empty(&dev->power.entry))
    + list_move_tail(&dev->power.entry, &dpm_prepared_list);
    + } else if (error == -EAGAIN) {
    + error = 0;
    + } else {
    dev_info(dev, "not prepared for power transition: code %d\n",
    error);
    - put_device(dev);
    - break;
    }
    - dev->power.is_prepared = true;
    - if (!list_empty(&dev->power.entry))
    - list_move_tail(&dev->power.entry, &dpm_prepared_list);
    +
    + mutex_unlock(&dpm_list_mtx);
    +
    put_device(dev);
    +
    + mutex_lock(&dpm_list_mtx);
    }
    mutex_unlock(&dpm_list_mtx);
    trace_suspend_resume(TPS("dpm_prepare"), state.event, false);

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