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ring-buffer: Clean ring_buffer_poll_wait() error return

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commit 66bbea9ed6 upstream.

The return type for ring_buffer_poll_wait() is __poll_t. This is behind
the scenes an unsigned where we can set event bits. In case of a
non-allocated CPU, we do return instead -EINVAL (0xffffffea). Lucky us,
this ends up setting few error bits (EPOLLERR | EPOLLHUP | EPOLLNVAL), so
user-space at least is aware something went wrong.

Nonetheless, this is an incorrect code. Replace that -EINVAL with a
proper EPOLLERR to clean that output. As this doesn't change the
behaviour, there's no need to treat this change as a bug fix.

Link: https://lore.kernel.org/linux-trace-kernel/[email protected]

Cc: [email protected]
Fixes: 6721cb6002 ("ring-buffer: Do not poll non allocated cpu buffers")
Signed-off-by: Vincent Donnefort <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Vincent Donnefort
2024-02-23 09:25:08 +01:00
committed by Greg Kroah-Hartman
parent 22a77c0f5b
commit f5f6332f18
1 changed files with 1 additions and 1 deletions
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kernel/trace/ring_buffer.c
+1 -1
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@@ -1091,7 +1091,7 @@ __poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
full = 0;
} else {
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return -EINVAL;
return EPOLLERR;
cpu_buffer = buffer->buffers[cpu];
work = &cpu_buffer->irq_work;