atomics: Constify loads

In order to match reality, allow using these functions with pointers on
const objects, and bring us closer to C11.

Remove the '+' modifier in the atomic_load_acq_64_i586()'s

atomics: Constify loads

In order to match reality, allow using these functions with pointers on
const objects, and bring us closer to C11.

Remove the '+' modifier in the atomic_load_acq_64_i586()'s inline asm
statement's constraint for '*p' (the value to load). CMPXCHG8B always
writes back some value, even when the value exchange does not happen in
which case what was read is written back. atomic_load_acq_64_i586()
further takes care of the operation atomically writing back the same
value that was read in any case. All in all, this makes the inline
asm's write back undetectable by any other code, whether executing on
other CPUs or code on the same CPU before and after the call to
atomic_load_acq_64_i586(), except for the fact that CMPXCHG8B will
trigger a #GP(0) if the memory address is part of a read-only mapping.
This unfortunate property is however out of scope of the C abstract
machine, and in particular independent of whether the 'uint64_t' pointed
to is declared 'const' or not.

Approved by: markj (mentor)
MFC after: 5 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D46887

show more ...

sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

show more ...

sys: clean up empty lines in .c and .h files

[PowerPC] [MIPS] Implement 32-bit kernel emulation of atomic64 operations

This is a lock-based emulation of 64-bit atomics for kernel use, split off
from an earlier patch by jhibbits.

This is neede

[PowerPC] [MIPS] Implement 32-bit kernel emulation of atomic64 operations

This is a lock-based emulation of 64-bit atomics for kernel use, split off
from an earlier patch by jhibbits.

This is needed to unblock future improvements that reduce the need for
locking on 64-bit platforms by using atomic updates.

The implementation allows for future integration with userland atomic64,
but as that implies going through sysarch for every use, the current
status quo of userland doing its own locking may be for the best.

Submitted by: jhibbits (original patch), kevans (mips bits)
Reviewed by: jhibbits, jeff, kevans
Differential Revision: https://reviews.freebsd.org/D22976

show more ...

atomics: Constify loads

In order to match reality, allow using these functions with pointers on
const objects, and bring us closer to C11.

Remove the '+' modifier in the atomic_load_acq_64_i586()'s

atomics: Constify loads

In order to match reality, allow using these functions with pointers on
const objects, and bring us closer to C11.

Remove the '+' modifier in the atomic_load_acq_64_i586()'s inline asm
statement's constraint for '*p' (the value to load). CMPXCHG8B always
writes back some value, even when the value exchange does not happen in
which case what was read is written back. atomic_load_acq_64_i586()
further takes care of the operation atomically writing back the same
value that was read in any case. All in all, this makes the inline
asm's write back undetectable by any other code, whether executing on
other CPUs or code on the same CPU before and after the call to
atomic_load_acq_64_i586(), except for the fact that CMPXCHG8B will
trigger a #GP(0) if the memory address is part of a read-only mapping.
This unfortunate property is however out of scope of the C abstract
machine, and in particular independent of whether the 'uint64_t' pointed
to is declared 'const' or not.

Approved by: markj (mentor)
MFC after: 5 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D46887

show more ...

sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

show more ...

sys: clean up empty lines in .c and .h files

[PowerPC] [MIPS] Implement 32-bit kernel emulation of atomic64 operations

This is a lock-based emulation of 64-bit atomics for kernel use, split off
from an earlier patch by jhibbits.

This is neede

[PowerPC] [MIPS] Implement 32-bit kernel emulation of atomic64 operations

This is a lock-based emulation of 64-bit atomics for kernel use, split off
from an earlier patch by jhibbits.

This is needed to unblock future improvements that reduce the need for
locking on 64-bit platforms by using atomic updates.

The implementation allows for future integration with userland atomic64,
but as that implies going through sysarch for every use, the current
status quo of userland doing its own locking may be for the best.

Submitted by: jhibbits (original patch), kevans (mips bits)
Reviewed by: jhibbits, jeff, kevans
Differential Revision: https://reviews.freebsd.org/D22976

show more ...

atomics: Constify loads

In order to match reality, allow using these functions with pointers on
const objects, and bring us closer to C11.

Remove the '+' modifier in the atomic_load_acq_64_i586()'s

atomics: Constify loads

In order to match reality, allow using these functions with pointers on
const objects, and bring us closer to C11.

Remove the '+' modifier in the atomic_load_acq_64_i586()'s inline asm
statement's constraint for '*p' (the value to load). CMPXCHG8B always
writes back some value, even when the value exchange does not happen in
which case what was read is written back. atomic_load_acq_64_i586()
further takes care of the operation atomically writing back the same
value that was read in any case. All in all, this makes the inline
asm's write back undetectable by any other code, whether executing on
other CPUs or code on the same CPU before and after the call to
atomic_load_acq_64_i586(), except for the fact that CMPXCHG8B will
trigger a #GP(0) if the memory address is part of a read-only mapping.
This unfortunate property is however out of scope of the C abstract
machine, and in particular independent of whether the 'uint64_t' pointed
to is declared 'const' or not.

Approved by: markj (mentor)
MFC after: 5 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D46887

show more ...

sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

show more ...

sys: clean up empty lines in .c and .h files

[PowerPC] [MIPS] Implement 32-bit kernel emulation of atomic64 operations

This is a lock-based emulation of 64-bit atomics for kernel use, split off
from an earlier patch by jhibbits.

This is neede

[PowerPC] [MIPS] Implement 32-bit kernel emulation of atomic64 operations

This is a lock-based emulation of 64-bit atomics for kernel use, split off
from an earlier patch by jhibbits.

This is needed to unblock future improvements that reduce the need for
locking on 64-bit platforms by using atomic updates.

The implementation allows for future integration with userland atomic64,
but as that implies going through sysarch for every use, the current
status quo of userland doing its own locking may be for the best.

Submitted by: jhibbits (original patch), kevans (mips bits)
Reviewed by: jhibbits, jeff, kevans
Differential Revision: https://reviews.freebsd.org/D22976

show more ...