commit d90b88fd3653f1fb66ecc6571b860d5a5749fa56 upstream.

Stack unwinding is implemented incorrectly in xtensa get_wchan: instead
of extracting a0 and a1 registers from the spill location under the
stack pointer it extracts a word pointed to by the stack pointer and
subtracts 4 or 3 from it.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This fixes the following warning at boot when the kernel is booted on a
board with more CPU cores than was configured in NR_CPUS:

  smp_init_cpus: Core Count = 8
  smp_init_cpus: Core Id = 0
  ------------[ cut here ]------------
  WARNING: CPU: 0 PID: 0 at include/linux/cpumask.h:121 smp_init_cpus+0x54/0x74
  Modules linked in:
  CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc3-00015-g1459333f88a0 #124
  Call Trace:
    __warn$part$3+0x6a/0x7c
    warn_slowpath_null+0x35/0x3c
    smp_init_cpus+0x54/0x74
    setup_arch+0x1c0/0x1d0
    start_kernel+0x44/0x310
    _startup+0x107/0x107

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

When building some xtensa config, I hit the following warning:
  drivers/staging/mt7621-dts/Kconfig:4:warning: 'BUILTIN_DTB' has wrong type.
  'select' only accept arguments of bool and tristate type

It is due to some arch use BUILTIN_DTB as a flag for the need to builtin
dtb but xtensa use it as a string for which dtb to bulltin.
But for this (which dtb to build), it is better to use
BUILTIN_DTB_SOURCE like other arch do.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

This patch fix a simple typo.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Otherwise it is impossible to enable CPUs after booting with 'maxcpus'
parameter.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Secondary CPU reset vector overlaps part of the double exception handler
code, resulting in weird crashes and hangups when running user code.
Move exception vectors one page up so that they don't clash with the
secondary CPU reset vector.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

- add missing memory barriers to the secondary CPU synchronization spin
  loops; add comment to the matching memory barrier in the boot_secondary
  and __cpu_die functions;
- use READ_ONCE/WRITE_ONCE to access cpu_start_id/cpu_start_ccount
  instead of reading/writing them directly;
- re-initialize cpu_running every time before starting secondary CPU to
  flush possible previous CPU startup results.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

ccount_timer_shutdown is called from the atomic context in the
secondary_start_kernel, resulting in the following BUG:

BUG: sleeping function called from invalid context
in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: swapper/1
Preemption disabled at:
  secondary_start_kernel+0xa1/0x130
Call Trace:
  ___might_sleep+0xe7/0xfc
  __might_sleep+0x41/0x44
  synchronize_irq+0x24/0x64
  disable_irq+0x11/0x14
  ccount_timer_shutdown+0x12/0x20
  clockevents_switch_state+0x82/0xb4
  clockevents_exchange_device+0x54/0x60
  tick_check_new_device+0x46/0x70
  clockevents_register_device+0x8c/0xc8
  clockevents_config_and_register+0x1d/0x2c
  local_timer_setup+0x75/0x7c
  secondary_start_kernel+0xb4/0x130
  should_never_return+0x32/0x35

Use disable_irq_nosync instead of disable_irq to avoid it.
This is safe because the ccount timer IRQ is per-CPU, and once IRQ is
masked the ISR will not be called.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Now that Kbuild automatically creates asm-generic wrappers for missing
mandatory headers, it is redundant to list the same headers in
generic-y and mandatory-y.

Suggested-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>

These comments are leftovers of commit fcc8487d477a ("uapi: export all
headers under uapi directories").

Prior to that commit, exported headers must be explicitly added to
header-y. Now, all headers under the uapi/ directories are exported.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>