linux.git/arch/arc/kernel/smp.c, branch v6.0

profile: setup_profiling_timer() is moslty not implemented

2022-07-30T01:12:36+00:00

The setup_profiling_timer() is mostly un-implemented by many
architectures.  In many places it isn't guarded by CONFIG_PROFILE which is
needed for it to be used.  Make it a weak symbol in kernel/profile.c and
remove the 'return -EINVAL' implementations from the kenrel.

There are a couple of architectures which do return 0 from the
setup_profiling_timer() function but they don't seem to do anything else
with it.  To keep the /proc compatibility for now, leave these for a
future update or removal.

On ARM, this fixes the following sparse warning:
arch/arm/kernel/smp.c:793:5: warning: symbol 'setup_profiling_timer' was not declared. Should it be static?

Link: https://lkml.kernel.org/r/20220721195509.418205-1-ben-linux@fluff.org
Signed-off-by: Ben Dooks 
Signed-off-by: Andrew Morton

ARC: remove redundant READ_ONCE() in cmpxchg loop

2022-04-18T21:47:05+00:00

This patch reverts commit 7082a29c22ac ("ARC: use ACCESS_ONCE in cmpxchg
loop").

It is not necessary to use READ_ONCE() because cmpxchg contains barrier. We
can get it from commit d57f727264f1 ("ARC: add compiler barrier to LLSC
based cmpxchg").

Signed-off-by: Bang Li 
Signed-off-by: Vineet Gupta

ARC: fix typos in comments

2022-04-18T19:20:23+00:00

Various spelling mistakes in comments.
Detected with the help of Coccinelle.

Signed-off-by: Julia Lawall 
Signed-off-by: Vineet Gupta

ARC: switch to generic bitops

2021-08-24T21:25:47+00:00

 - !LLSC now only needs a single spinlock for atomics and bitops

 - Some codegen changes (slight bloat) with generic bitops

   1. code increase due to LD-check-atomic paradigm vs. unconditonal
      atomic (but dirty'ing the cache line even if set already).
      So despite increase, generic is right thing to do.

   2. code decrease (but use of costlier instructions such as DIV vs.
      shifts based math) due to signed arithmetic.
      This needs to be revisited seperately.

     arc:
     static inline int test_bit(unsigned int nr, const volatile unsigned long *addr)
                                ^^^^^^^^^^^^
     generic:
     static inline int test_bit(int nr, const volatile unsigned long *addr)
                                ^^^

Link: https://lore.kernel.org/r/20180830135749.GA13005@arm.com
Signed-off-by: Will Deacon 
Acked-by: Peter Zijlstra (Intel) 
[vgupta: wrote patch based on Will's poc, analysed codegen diffs]
Signed-off-by: Vineet Gupta

arch/arc/kernel/: fix misspellings using codespell tool

2021-08-24T21:25:46+00:00

Some typos are found out by codespell tool:

./intc-compact.c:145: prioity ==> priority
./smp.c:286: recevier ==> receiver
./stacktrace.c:152 prelogue ==> prologue

Fix typos found by codespell.

Reported-by: Zeal Robot 
Signed-off-by: Changcheng Deng 
Signed-off-by: Yi Wang 
Signed-off-by: Vineet Gupta

sched/core: Initialize the idle task with preemption disabled

2021-05-12T11:01:45+00:00

As pointed out by commit

  de9b8f5dcbd9 ("sched: Fix crash trying to dequeue/enqueue the idle thread")

init_idle() can and will be invoked more than once on the same idle
task. At boot time, it is invoked for the boot CPU thread by
sched_init(). Then smp_init() creates the threads for all the secondary
CPUs and invokes init_idle() on them.

As the hotplug machinery brings the secondaries to life, it will issue
calls to idle_thread_get(), which itself invokes init_idle() yet again.
In this case it's invoked twice more per secondary: at _cpu_up(), and at
bringup_cpu().

Given smp_init() already initializes the idle tasks for all *possible*
CPUs, no further initialization should be required. Now, removing
init_idle() from idle_thread_get() exposes some interesting expectations
with regards to the idle task's preempt_count: the secondary startup always
issues a preempt_disable(), requiring some reset of the preempt count to 0
between hot-unplug and hotplug, which is currently served by
idle_thread_get() -> idle_init().

Given the idle task is supposed to have preemption disabled once and never
see it re-enabled, it seems that what we actually want is to initialize its
preempt_count to PREEMPT_DISABLED and leave it there. Do that, and remove
init_idle() from idle_thread_get().

Secondary startups were patched via coccinelle:

  @begone@
  @@

  -preempt_disable();
  ...
  cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);

Signed-off-by: Valentin Schneider 
Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com

ARC: SMP: fix typo and use "come up" instead of "comeup"

2020-10-06T04:02:29+00:00

When a secondary CPU fails to come up, there is a missing space in the
log:

	Timeout: CPU1 FAILED to comeup !!!

Fix it.

Signed-off-by: Mike Rapoport 
Signed-off-by: Vineet Gupta

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500

2019-06-19T15:09:55+00:00

Based on 2 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Enrico Weigelt 
Reviewed-by: Kate Stewart 
Reviewed-by: Allison Randal 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman

ARC: setup cpu possible mask according to possible-cpus dts property

2018-02-28T18:45:32+00:00

As we have option in u-boot to set CPU mask for running linux,
we want to pass information to kernel about CPU cores should
be brought up. So we patch kernel dtb in u-boot to set
possible-cpus property.

This also allows us to have correctly setuped MCIP debug mask.

Signed-off-by: Eugeniy Paltsev 
Signed-off-by: Vineet Gupta

Merge branch 'linus' into locking/core, to resolve conflicts

2017-11-07T09:32:44+00:00

Conflicts:
	include/linux/compiler-clang.h
	include/linux/compiler-gcc.h
	include/linux/compiler-intel.h
	include/uapi/linux/stddef.h

Signed-off-by: Ingo Molnar