From 1df8091e631b72df8ecda105dae7934b54b1287c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Barnab=C3=A1s=20P=C5=91cze?=
<barnabas.pocze@ideasonboard.com>
Date: Fri, 7 Mar 2025 16:00:21 +0100
Subject: libcamera: v4l2_videodevice: `lastUsedCounter_` need not be atomic
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The `V4L2BufferCache` type is not thread-safe. Its `lastUsedCounter_`
member is not used in contexts where its atomicity would matter.
So it does not need to be have an atomic type.
Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
include/libcamera/internal/v4l2_videodevice.h | 3 +--
src/libcamera/v4l2_videodevice.cpp | 4 ++--
2 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/include/libcamera/internal/v4l2_videodevice.h b/include/libcamera/internal/v4l2_videodevice.h
index f021c2a0..ae6a76cb 100644
--- a/include/libcamera/internal/v4l2_videodevice.h
+++ b/include/libcamera/internal/v4l2_videodevice.h
@@ -8,7 +8,6 @@
#pragma once
#include <array>
-#include <atomic>
#include <memory>
#include <optional>
#include <ostream>
@@ -158,7 +157,7 @@ private:
std::vector<Plane> planes_;
};
- std::atomic<uint64_t> lastUsedCounter_;
+ uint64_t lastUsedCounter_;
std::vector<Entry> cache_;
/* \todo Expose the miss counter through an instrumentation API. */
unsigned int missCounter_;
diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index e241eb47..f5b3fa09 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -190,7 +190,7 @@ V4L2BufferCache::V4L2BufferCache(const std::vector<std::unique_ptr<FrameBuffer>>
{
for (const std::unique_ptr<FrameBuffer> &buffer : buffers)
cache_.emplace_back(true,
- lastUsedCounter_.fetch_add(1, std::memory_order_acq_rel),
+ lastUsedCounter_++,
*buffer.get());
}
@@ -258,7 +258,7 @@ int V4L2BufferCache::get(const FrameBuffer &buffer)
return -ENOENT;
cache_[use] = Entry(false,
- lastUsedCounter_.fetch_add(1, std::memory_order_acq_rel),
+ lastUsedCounter_++,
buffer);
return use;
--
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