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kernel/block_cache: Minor code cleanup, and add a comment.

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Detailing how we avoid use-after-frees in get_cached_block when reads
fail.
This commit is contained in:
Augustin Cavalier 2024-11-19 18:14:29 -05:00
parent d8914ec8b0
commit 4550b3c025
1 changed files with 4 additions and 9 deletions
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13
src/system/kernel/cache/block_cache.cpp vendored
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@ -1998,7 +1998,7 @@ mark_block_unbusy_reading(block_cache* cache, cached_block* block)
cache->busy_reading_count--;
if ((cache->busy_reading_waiters && cache->busy_reading_count == 0)
|| block->busy_reading_waiters) {
|| block->busy_reading_waiters) {
cache->busy_reading_waiters = false;
block->busy_reading_waiters = false;
cache->busy_reading_condition.NotifyAll();
@ -2018,9 +2018,7 @@ wait_for_busy_reading_block(block_cache* cache, cached_block* block)
block->busy_reading_waiters = true;
mutex_unlock(&cache->lock);
entry.Wait();
mutex_lock(&cache->lock);
}
}
@ -2038,9 +2036,7 @@ wait_for_busy_reading_blocks(block_cache* cache)
cache->busy_reading_waiters = true;
mutex_unlock(&cache->lock);
entry.Wait();
mutex_lock(&cache->lock);
}
}
@ -2058,9 +2054,7 @@ wait_for_busy_writing_block(block_cache* cache, cached_block* block)
block->busy_writing_waiters = true;
mutex_unlock(&cache->lock);
entry.Wait();
mutex_lock(&cache->lock);
}
}
@ -2078,9 +2072,7 @@ wait_for_busy_writing_blocks(block_cache* cache)
cache->busy_writing_waiters = true;
mutex_unlock(&cache->lock);
entry.Wait();
mutex_lock(&cache->lock);
}
}
@ -2190,6 +2182,9 @@ retry:
} else if (block->busy_reading) {
// The block is currently busy_reading - wait and try again later
wait_for_busy_reading_block(cache, block);
// The block may have been deleted or replaced in the meantime,
// so we must look it up in the hash again after waiting.
goto retry;
}