treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of th

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174

Based on 1 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
distributed in the hope that it will be useful but without any
warranty without even the implied warranty of merchantability or
fitness for a particular purpose see the gnu general public license
for more details

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 655 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070034.575739538@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

ARM: mcpm: Add baremetal voting mutexes

This patch adds a simple low-level voting mutex implementation
to be used to arbitrate during first man selection when no load/store
exclusive instructions ar

ARM: mcpm: Add baremetal voting mutexes

This patch adds a simple low-level voting mutex implementation
to be used to arbitrate during first man selection when no load/store
exclusive instructions are usable.

For want of a better name, these are called "vlocks". (I was
tempted to call them ballot locks, but "block" is way too confusing
an abbreviation...)

There is no function to wait for the lock to be released, and no
vlock_lock() function since we don't need these at the moment.
These could straightforwardly be added if vlocks get used for other
purposes.

For architectural correctness even Strongly-Ordered memory accesses
require barriers in order to guarantee that multiple CPUs have a
coherent view of the ordering of memory accesses. Whether or not
this matters depends on hardware implementation details of the
memory system. Since the purpose of this code is to provide a clean,
generic locking mechanism with no platform-specific dependencies the
barriers should be present to avoid unpleasant surprises on future
platforms.

Note:

* When taking the lock, we don't care about implicit background
memory operations and other signalling which may be pending,
because those are not part of the critical section anyway.

A DMB is sufficient to ensure correctly observed ordering if
the explicit memory accesses in vlock_trylock.

* No barrier is required after checking the election result,
because the result is determined by the store to
VLOCK_OWNER_OFFSET and is already globally observed due to the
barriers in voting_end. This means that global agreement on
the winner is guaranteed, even before the winner is known
locally.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>

show more ...

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it u

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174

Based on 1 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
distributed in the hope that it will be useful but without any
warranty without even the implied warranty of merchantability or
fitness for a particular purpose see the gnu general public license
for more details

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 655 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070034.575739538@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

ARM: mcpm: Add baremetal voting mutexes

This patch adds a simple low-level voting mutex implementation
to be used to arbitrate during first man selection when no load/store
exclusive

ARM: mcpm: Add baremetal voting mutexes

This patch adds a simple low-level voting mutex implementation
to be used to arbitrate during first man selection when no load/store
exclusive instructions are usable.

For want of a better name, these are called "vlocks". (I was
tempted to call them ballot locks, but "block" is way too confusing
an abbreviation...)

There is no function to wait for the lock to be released, and no
vlock_lock() function since we don't need these at the moment.
These could straightforwardly be added if vlocks get used for other
purposes.

For architectural correctness even Strongly-Ordered memory accesses
require barriers in order to guarantee that multiple CPUs have a
coherent view of the ordering of memory accesses. Whether or not
this matters depends on hardware implementation details of the
memory system. Since the purpose of this code is to provide a clean,
generic locking mechanism with no platform-specific dependencies the
barriers should be present to avoid unpleasant surprises on future
platforms.

Note:

* When taking the lock, we don't care about implicit background
memory operations and other signalling which may be pending,
because those are not part of the critical section anyway.

A DMB is sufficient to ensure correctly observed ordering if
the explicit memory accesses in vlock_trylock.

* No barrier is required after checking the election result,
because the result is determined by the store to
VLOCK_OWNER_OFFSET and is already globally observed due to the
barriers in voting_end. This means that global agreement on
the winner is guaranteed, even before the winner is known
locally.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>

show more ...