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Andrea Righi 27af8e2c90 leds: trigger: fix potential deadlock with libata 
We have the following potential deadlock condition:

 ========================================================
 WARNING: possible irq lock inversion dependency detected
 5.10.0-rc2+ #25 Not tainted
 --------------------------------------------------------
 swapper/3/0 just changed the state of lock:
 ffff8880063bd618 (&host->lock){-...}-{2:2}, at: ata_bmdma_interrupt+0x27/0x200
 but this lock took another, HARDIRQ-READ-unsafe lock in the past:
  (&trig->leddev_list_lock){.+.?}-{2:2}

 and interrupts could create inverse lock ordering between them.

 other info that might help us debug this:
  Possible interrupt unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&trig->leddev_list_lock);
                                local_irq_disable();
                                lock(&host->lock);
                                lock(&trig->leddev_list_lock);
   <Interrupt>
     lock(&host->lock);

  *** DEADLOCK ***

 no locks held by swapper/3/0.

 the shortest dependencies between 2nd lock and 1st lock:
  -> (&trig->leddev_list_lock){.+.?}-{2:2} ops: 46 {
     HARDIRQ-ON-R at:
                       lock_acquire+0x15f/0x420
                       _raw_read_lock+0x42/0x90
                       led_trigger_event+0x2b/0x70
                       rfkill_global_led_trigger_worker+0x94/0xb0
                       process_one_work+0x240/0x560
                       worker_thread+0x58/0x3d0
                       kthread+0x151/0x170
                       ret_from_fork+0x1f/0x30
     IN-SOFTIRQ-R at:
                       lock_acquire+0x15f/0x420
                       _raw_read_lock+0x42/0x90
                       led_trigger_event+0x2b/0x70
                       kbd_bh+0x9e/0xc0
                       tasklet_action_common.constprop.0+0xe9/0x100
                       tasklet_action+0x22/0x30
                       __do_softirq+0xcc/0x46d
                       run_ksoftirqd+0x3f/0x70
                       smpboot_thread_fn+0x116/0x1f0
                       kthread+0x151/0x170
                       ret_from_fork+0x1f/0x30
     SOFTIRQ-ON-R at:
                       lock_acquire+0x15f/0x420
                       _raw_read_lock+0x42/0x90
                       led_trigger_event+0x2b/0x70
                       rfkill_global_led_trigger_worker+0x94/0xb0
                       process_one_work+0x240/0x560
                       worker_thread+0x58/0x3d0
                       kthread+0x151/0x170
                       ret_from_fork+0x1f/0x30
     INITIAL READ USE at:
                           lock_acquire+0x15f/0x420
                           _raw_read_lock+0x42/0x90
                           led_trigger_event+0x2b/0x70
                           rfkill_global_led_trigger_worker+0x94/0xb0
                           process_one_work+0x240/0x560
                           worker_thread+0x58/0x3d0
                           kthread+0x151/0x170
                           ret_from_fork+0x1f/0x30
   }
   ... key      at: [<ffffffff83da4c00>] __key.0+0x0/0x10
   ... acquired at:
    _raw_read_lock+0x42/0x90
    led_trigger_blink_oneshot+0x3b/0x90
    ledtrig_disk_activity+0x3c/0xa0
    ata_qc_complete+0x26/0x450
    ata_do_link_abort+0xa3/0xe0
    ata_port_freeze+0x2e/0x40
    ata_hsm_qc_complete+0x94/0xa0
    ata_sff_hsm_move+0x177/0x7a0
    ata_sff_pio_task+0xc7/0x1b0
    process_one_work+0x240/0x560
    worker_thread+0x58/0x3d0
    kthread+0x151/0x170
    ret_from_fork+0x1f/0x30

 -> (&host->lock){-...}-{2:2} ops: 69 {
    IN-HARDIRQ-W at:
                     lock_acquire+0x15f/0x420
                     _raw_spin_lock_irqsave+0x52/0xa0
                     ata_bmdma_interrupt+0x27/0x200
                     __handle_irq_event_percpu+0xd5/0x2b0
                     handle_irq_event+0x57/0xb0
                     handle_edge_irq+0x8c/0x230
                     asm_call_irq_on_stack+0xf/0x20
                     common_interrupt+0x100/0x1c0
                     asm_common_interrupt+0x1e/0x40
                     native_safe_halt+0xe/0x10
                     arch_cpu_idle+0x15/0x20
                     default_idle_call+0x59/0x1c0
                     do_idle+0x22c/0x2c0
                     cpu_startup_entry+0x20/0x30
                     start_secondary+0x11d/0x150
                     secondary_startup_64_no_verify+0xa6/0xab
    INITIAL USE at:
                    lock_acquire+0x15f/0x420
                    _raw_spin_lock_irqsave+0x52/0xa0
                    ata_dev_init+0x54/0xe0
                    ata_link_init+0x8b/0xd0
                    ata_port_alloc+0x1f1/0x210
                    ata_host_alloc+0xf1/0x130
                    ata_host_alloc_pinfo+0x14/0xb0
                    ata_pci_sff_prepare_host+0x41/0xa0
                    ata_pci_bmdma_prepare_host+0x14/0x30
                    piix_init_one+0x21f/0x600
                    local_pci_probe+0x48/0x80
                    pci_device_probe+0x105/0x1c0
                    really_probe+0x221/0x490
                    driver_probe_device+0xe9/0x160
                    device_driver_attach+0xb2/0xc0
                    __driver_attach+0x91/0x150
                    bus_for_each_dev+0x81/0xc0
                    driver_attach+0x1e/0x20
                    bus_add_driver+0x138/0x1f0
                    driver_register+0x91/0xf0
                    __pci_register_driver+0x73/0x80
                    piix_init+0x1e/0x2e
                    do_one_initcall+0x5f/0x2d0
                    kernel_init_freeable+0x26f/0x2cf
                    kernel_init+0xe/0x113
                    ret_from_fork+0x1f/0x30
  }
  ... key      at: [<ffffffff83d9fdc0>] __key.6+0x0/0x10
  ... acquired at:
    __lock_acquire+0x9da/0x2370
    lock_acquire+0x15f/0x420
    _raw_spin_lock_irqsave+0x52/0xa0
    ata_bmdma_interrupt+0x27/0x200
    __handle_irq_event_percpu+0xd5/0x2b0
    handle_irq_event+0x57/0xb0
    handle_edge_irq+0x8c/0x230
    asm_call_irq_on_stack+0xf/0x20
    common_interrupt+0x100/0x1c0
    asm_common_interrupt+0x1e/0x40
    native_safe_halt+0xe/0x10
    arch_cpu_idle+0x15/0x20
    default_idle_call+0x59/0x1c0
    do_idle+0x22c/0x2c0
    cpu_startup_entry+0x20/0x30
    start_secondary+0x11d/0x150
    secondary_startup_64_no_verify+0xa6/0xab

This lockdep splat is reported after:
commit e918188611 ("locking: More accurate annotations for read_lock()")

To clarify:
 - read-locks are recursive only in interrupt context (when
   in_interrupt() returns true)
 - after acquiring host->lock in CPU1, another cpu (i.e. CPU2) may call
   write_lock(&trig->leddev_list_lock) that would be blocked by CPU0
   that holds trig->leddev_list_lock in read-mode
 - when CPU1 (ata_ac_complete()) tries to read-lock
   trig->leddev_list_lock, it would be blocked by the write-lock waiter
   on CPU2 (because we are not in interrupt context, so the read-lock is
   not recursive)
 - at this point if an interrupt happens on CPU0 and
   ata_bmdma_interrupt() is executed it will try to acquire host->lock,
   that is held by CPU1, that is currently blocked by CPU2, so:

   * CPU0 blocked by CPU1
   * CPU1 blocked by CPU2
   * CPU2 blocked by CPU0

     *** DEADLOCK ***

The deadlock scenario is better represented by the following schema
(thanks to Boqun Feng <boqun.feng@gmail.com> for the schema and the
detailed explanation of the deadlock condition):

 CPU 0:                          CPU 1:                        CPU 2:
 -----                           -----                         -----
 led_trigger_event():
   read_lock(&trig->leddev_list_lock);
 				<workqueue>
 				ata_hsm_qc_complete():
 				  spin_lock_irqsave(&host->lock);
 								write_lock(&trig->leddev_list_lock);
 				  ata_port_freeze():
 				    ata_do_link_abort():
 				      ata_qc_complete():
 					ledtrig_disk_activity():
 					  led_trigger_blink_oneshot():
 					    read_lock(&trig->leddev_list_lock);
 					    // ^ not in in_interrupt() context, so could get blocked by CPU 2
 <interrupt>
   ata_bmdma_interrupt():
     spin_lock_irqsave(&host->lock);

Fix by using read_lock_irqsave/irqrestore() in led_trigger_event(), so
that no interrupt can happen in between, preventing the deadlock
condition.

Apply the same change to led_trigger_blink_setup() as well, since the
same deadlock scenario can also happen in power_supply_update_bat_leds()
-> led_trigger_blink() -> led_trigger_blink_setup() (workqueue context),
and potentially prevent other similar usages.

Link: https://lore.kernel.org/lkml/20201101092614.GB3989@xps-13-7390/
Fixes: eb25cb9956 ("leds: convert IDE trigger to common disk trigger")
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
2021-01-31 10:38:03 +01:00
arch RISC-V Fixes for 5.11-rc1 2020-12-24 14:05:05 -08:00
block block: update some copyrights 2020-12-22 08:43:06 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto crypto: aegis128 - avoid spurious references crypto_aegis128_update_simd 2020-12-04 18:16:53 +11:00
Documentation A small set of late-arriving, small documentation fixes. 2020-12-24 14:20:33 -08:00
drivers leds: trigger: fix potential deadlock with libata 2021-01-31 10:38:03 +01:00
fs proc mountinfo: make splice available again 2020-12-27 12:00:36 -08:00
include Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-12-25 10:54:29 -08:00
init kasan, arm64: only use kasan_depth for software modes 2020-12-22 12:55:07 -08:00
ipc Merge branch 'akpm' (patches from Andrew) 2020-12-15 12:53:37 -08:00
kernel Misc fixes/updates: 2020-12-27 09:06:10 -08:00
lib kasan: introduce CONFIG_KASAN_HW_TAGS 2020-12-22 12:55:07 -08:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm virtio,vdpa: features, cleanups, fixes 2020-12-24 12:06:46 -08:00
net 9p for 5.11-rc1 2020-12-21 10:28:02 -08:00
samples ARM: SoC drivers for v5.11 2020-12-16 16:38:41 -08:00
scripts Merge branch 'for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/jlawall/linux 2020-12-25 11:05:32 -08:00
security Provide a fix for the incorrect handling of privilege 2020-12-24 14:08:43 -08:00
sound sound fixes for 5.11-rc1 2020-12-23 15:11:08 -08:00
tools Fix a segfault that occurs when built with Clang. 2020-12-27 09:08:23 -08:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt ARM: 2020-12-20 10:44:05 -08:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
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.mailmap RDMA 5.11 pull request 2020-12-16 13:42:26 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-12-11 22:29:38 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Misc fixes/updates: 2020-12-27 09:06:10 -08:00
Makefile Linux 5.11-rc1 2020-12-27 15:30:22 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

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.