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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-06-19 21:00:30 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-06-19 21:00:30 +0000 |
commit | e54def4ad8144ab15f826416e2e0f290ef1901b4 (patch) | |
tree | 583f8d4bd95cd67c44ff37b878a7eddfca9ab97a /Documentation/scheduler/membarrier.rst | |
parent | Adding upstream version 6.8.12. (diff) | |
download | linux-e54def4ad8144ab15f826416e2e0f290ef1901b4.tar.xz linux-e54def4ad8144ab15f826416e2e0f290ef1901b4.zip |
Adding upstream version 6.9.2.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/scheduler/membarrier.rst')
-rw-r--r-- | Documentation/scheduler/membarrier.rst | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/Documentation/scheduler/membarrier.rst b/Documentation/scheduler/membarrier.rst new file mode 100644 index 0000000000..2387804b1c --- /dev/null +++ b/Documentation/scheduler/membarrier.rst @@ -0,0 +1,39 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================== +membarrier() System Call +======================== + +MEMBARRIER_CMD_{PRIVATE,GLOBAL}_EXPEDITED - Architecture requirements +===================================================================== + +Memory barriers before updating rq->curr +---------------------------------------- + +The commands MEMBARRIER_CMD_PRIVATE_EXPEDITED and MEMBARRIER_CMD_GLOBAL_EXPEDITED +require each architecture to have a full memory barrier after coming from +user-space, before updating rq->curr. This barrier is implied by the sequence +rq_lock(); smp_mb__after_spinlock() in __schedule(). The barrier matches a full +barrier in the proximity of the membarrier system call exit, cf. +membarrier_{private,global}_expedited(). + +Memory barriers after updating rq->curr +--------------------------------------- + +The commands MEMBARRIER_CMD_PRIVATE_EXPEDITED and MEMBARRIER_CMD_GLOBAL_EXPEDITED +require each architecture to have a full memory barrier after updating rq->curr, +before returning to user-space. The schemes providing this barrier on the various +architectures are as follows. + + - alpha, arc, arm, hexagon, mips rely on the full barrier implied by + spin_unlock() in finish_lock_switch(). + + - arm64 relies on the full barrier implied by switch_to(). + + - powerpc, riscv, s390, sparc, x86 rely on the full barrier implied by + switch_mm(), if mm is not NULL; they rely on the full barrier implied + by mmdrop(), otherwise. On powerpc and riscv, switch_mm() relies on + membarrier_arch_switch_mm(). + +The barrier matches a full barrier in the proximity of the membarrier system call +entry, cf. membarrier_{private,global}_expedited(). |