Hello Subversion Developers, Following up on our recent investigation into svnserve (1.14.x) crashes in high-load environments (linked to our report on SVN-4817), we have identified a third, distinct race condition in the logging implementation in subversion/svnserve/logger.c.
Problem Description: In log_message(), the code performs memory allocations from the shared logger->pool before acquiring the serialization mutex (logger->mutex). When multiple threads encounter errors simultaneously (a frequent occurrence during network congestion bursts), they attempt concurrent allocations from the same APR pool, leading to internal corruption and a SIGSEGV during the subsequent svn_pool_clear. Proposed Fix: The attached/in-lined patch moves the apr_palloc and svn_time_to_cstring calls inside the mutex lock. We have verified this fix in production; it has successfully stabilized our fleet under the same load conditions that previously triggered the crashes. -- Eric Boehm Broadcom
svnserve_log_concurrency.patch
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