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Sergey Senozhatsky 2e76a3a166 serial: 8250: change lock order in serial8250_do_startup() 
commit 205d300aea upstream.

We have a number of "uart.port->desc.lock vs desc.lock->uart.port"
lockdep reports coming from 8250 driver; this causes a bit of trouble
to people, so let's fix it.

The problem is reverse lock order in two different call paths:

chain #1:

 serial8250_do_startup()
  spin_lock_irqsave(&port->lock);
   disable_irq_nosync(port->irq);
    raw_spin_lock_irqsave(&desc->lock)

chain #2:

  __report_bad_irq()
   raw_spin_lock_irqsave(&desc->lock)
    for_each_action_of_desc()
     printk()
      spin_lock_irqsave(&port->lock);

Fix this by changing the order of locks in serial8250_do_startup():
 do disable_irq_nosync() first, which grabs desc->lock, and grab
 uart->port after that, so that chain #1 and chain #2 have same lock
 order.

Full lockdep splat:

 ======================================================
 WARNING: possible circular locking dependency detected
 5.4.39 #55 Not tainted
 ======================================================

 swapper/0/0 is trying to acquire lock:
 ffffffffab65b6c0 (console_owner){-...}, at: console_lock_spinning_enable+0x31/0x57

 but task is already holding lock:
 ffff88810a8e34c0 (&irq_desc_lock_class){-.-.}, at: __report_bad_irq+0x5b/0xba

 which lock already depends on the new lock.

 the existing dependency chain (in reverse order) is:

 -> #2 (&irq_desc_lock_class){-.-.}:
        _raw_spin_lock_irqsave+0x61/0x8d
        __irq_get_desc_lock+0x65/0x89
        __disable_irq_nosync+0x3b/0x93
        serial8250_do_startup+0x451/0x75c
        uart_startup+0x1b4/0x2ff
        uart_port_activate+0x73/0xa0
        tty_port_open+0xae/0x10a
        uart_open+0x1b/0x26
        tty_open+0x24d/0x3a0
        chrdev_open+0xd5/0x1cc
        do_dentry_open+0x299/0x3c8
        path_openat+0x434/0x1100
        do_filp_open+0x9b/0x10a
        do_sys_open+0x15f/0x3d7
        kernel_init_freeable+0x157/0x1dd
        kernel_init+0xe/0x105
        ret_from_fork+0x27/0x50

 -> #1 (&port_lock_key){-.-.}:
        _raw_spin_lock_irqsave+0x61/0x8d
        serial8250_console_write+0xa7/0x2a0
        console_unlock+0x3b7/0x528
        vprintk_emit+0x111/0x17f
        printk+0x59/0x73
        register_console+0x336/0x3a4
        uart_add_one_port+0x51b/0x5be
        serial8250_register_8250_port+0x454/0x55e
        dw8250_probe+0x4dc/0x5b9
        platform_drv_probe+0x67/0x8b
        really_probe+0x14a/0x422
        driver_probe_device+0x66/0x130
        device_driver_attach+0x42/0x5b
        __driver_attach+0xca/0x139
        bus_for_each_dev+0x97/0xc9
        bus_add_driver+0x12b/0x228
        driver_register+0x64/0xed
        do_one_initcall+0x20c/0x4a6
        do_initcall_level+0xb5/0xc5
        do_basic_setup+0x4c/0x58
        kernel_init_freeable+0x13f/0x1dd
        kernel_init+0xe/0x105
        ret_from_fork+0x27/0x50

 -> #0 (console_owner){-...}:
        __lock_acquire+0x118d/0x2714
        lock_acquire+0x203/0x258
        console_lock_spinning_enable+0x51/0x57
        console_unlock+0x25d/0x528
        vprintk_emit+0x111/0x17f
        printk+0x59/0x73
        __report_bad_irq+0xa3/0xba
        note_interrupt+0x19a/0x1d6
        handle_irq_event_percpu+0x57/0x79
        handle_irq_event+0x36/0x55
        handle_fasteoi_irq+0xc2/0x18a
        do_IRQ+0xb3/0x157
        ret_from_intr+0x0/0x1d
        cpuidle_enter_state+0x12f/0x1fd
        cpuidle_enter+0x2e/0x3d
        do_idle+0x1ce/0x2ce
        cpu_startup_entry+0x1d/0x1f
        start_kernel+0x406/0x46a
        secondary_startup_64+0xa4/0xb0

 other info that might help us debug this:

 Chain exists of:
   console_owner --> &port_lock_key --> &irq_desc_lock_class

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&irq_desc_lock_class);
                                lock(&port_lock_key);
                                lock(&irq_desc_lock_class);
   lock(console_owner);

  *** DEADLOCK ***

 2 locks held by swapper/0/0:
  #0: ffff88810a8e34c0 (&irq_desc_lock_class){-.-.}, at: __report_bad_irq+0x5b/0xba
  #1: ffffffffab65b5c0 (console_lock){+.+.}, at: console_trylock_spinning+0x20/0x181

 stack backtrace:
 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.4.39 #55
 Hardware name: XXXXXX
 Call Trace:
  <IRQ>
  dump_stack+0xbf/0x133
  ? print_circular_bug+0xd6/0xe9
  check_noncircular+0x1b9/0x1c3
  __lock_acquire+0x118d/0x2714
  lock_acquire+0x203/0x258
  ? console_lock_spinning_enable+0x31/0x57
  console_lock_spinning_enable+0x51/0x57
  ? console_lock_spinning_enable+0x31/0x57
  console_unlock+0x25d/0x528
  ? console_trylock+0x18/0x4e
  vprintk_emit+0x111/0x17f
  ? lock_acquire+0x203/0x258
  printk+0x59/0x73
  __report_bad_irq+0xa3/0xba
  note_interrupt+0x19a/0x1d6
  handle_irq_event_percpu+0x57/0x79
  handle_irq_event+0x36/0x55
  handle_fasteoi_irq+0xc2/0x18a
  do_IRQ+0xb3/0x157
  common_interrupt+0xf/0xf
  </IRQ>

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Fixes: 768aec0b5b ("serial: 8250: fix shared interrupts issues with SMP and RT kernels")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Reported-by: Raul Rangel <rrangel@google.com>
BugLink: https://bugs.chromium.org/p/chromium/issues/detail?id=1114800
Link: https://lore.kernel.org/lkml/CAHQZ30BnfX+gxjPm1DUd5psOTqbyDh4EJE=2=VAMW_VDafctkA@mail.gmail.com/T/#u
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200817022646.1484638-1-sergey.senozhatsky@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2020-09-03 11:27:04 +02:00
Documentation kbuild: support LLVM=1 to switch the default tools to Clang/LLVM 2020-08-26 10:40:47 +02:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch arm64: Allow booting of late CPUs affected by erratum 1418040 2020-09-03 11:27:01 +02:00
block blk-mq: order adding requests to hctx->dispatch and checking SCHED_RESTART 2020-09-03 11:27:01 +02:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: algif_aead - fix uninitialized ctx->init 2020-08-21 13:05:38 +02:00
drivers serial: 8250: change lock order in serial8250_do_startup() 2020-09-03 11:27:04 +02:00
fs btrfs: detect nocow for swap after snapshot delete 2020-09-03 11:27:02 +02:00
include netfilter: avoid ipv6 -> nf_defrag_ipv6 module dependency 2020-09-03 11:26:58 +02:00
init x86: Fix early boot crash on gcc-10, third try 2020-05-20 08:20:34 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel sched/uclamp: Fix a deadlock when enabling uclamp static key 2020-09-03 11:26:49 +02:00
lib test_kmod: avoid potential double free in trigger_config_run_type() 2020-08-21 13:05:37 +02:00
mm mm/vunmap: add cond_resched() in vunmap_pmd_range 2020-09-03 11:26:52 +02:00
net can: j1939: transport: j1939_xtp_rx_dat_one(): compare own packets to detect corruptions 2020-09-03 11:26:58 +02:00
samples bpf: Fix fds_example SIGSEGV error 2020-08-19 08:16:03 +02:00
scripts kconfig: qconf: fix signal connection to invalid slots 2020-08-26 10:41:04 +02:00
security Smack: prevent underflow in smk_set_cipso() 2020-08-19 08:16:16 +02:00
sound ASoC: wm8994: Avoid attempts to read unreadable registers 2020-09-03 11:26:59 +02:00
tools selftests: disable rp_filter for icmp_redirect.sh 2020-09-03 11:26:59 +02:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: arm64: Only reschedule if MMU_NOTIFIER_RANGE_BLOCKABLE is not set 2020-08-26 10:41:08 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
…
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.61 2020-08-26 10:41:08 +02:00
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.