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kernel/pipe: disable direct-to-readers copy with CONFIG_KERNEL_COHERENCE

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Systems that enabled this option don't have their stacks in coherent
memory. Given our pipe_buf_spec is stored on the stack, and readers may
also have their destination buffer on their stack too, it is not worth
going to the trouble of supporting direct-to-readers copy with them.

Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
This commit is contained in:
Nicolas Pitre 2025-01-18 13:01:23 -05:00 • committed by Benjamin Cabé
commit 0c0644bd68
1 changed files with 12 additions and 1 deletions
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13
kernel/pipe.c
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@ -162,7 +162,18 @@ int z_impl_k_pipe_write(struct k_pipe *pipe, const uint8_t *data, size_t len, k_
}
if (pipe_empty(pipe)) {
if (pipe->waiting != 0) {
if (IS_ENABLED(CONFIG_KERNEL_COHERENCE)) {
/*
* Systems that enabled this option don't have
* their stacks in coherent memory. Given our
* pipe_buf_spec is stored on the stack, and
* readers may also have their destination
* buffer on their stack too, it is not worth
* supporting direct-to-readers copy with them.
* Simply wake up all pending readers instead.
*/
need_resched = z_sched_wake_all(&pipe->data, 0, NULL);
} else if (pipe->waiting != 0) {
written += copy_to_pending_readers(pipe, &need_resched,
&data[written],
len - written);