mirror of
https://git.haproxy.org/git/haproxy.git/
synced 2026-02-15 22:31:29 +01:00
b2f38c13d1
A few loops waiting for threads to synchronize such as thread_isolate() rightfully filter the thread masks via the threads_enabled field that contains the list of enabled threads. However, it doesn't use an atomic load on it. Before 2.7, the equivalent variables were marked as volatile and were always reloaded. In 2.7 they're fields in ha_tgroup_ctx[], and the risk that the compiler keeps them in a register inside a loop is not null at all. In practice when ha_thread_relax() calls sched_yield() or an x86 PAUSE instruction, it could be verified that the variable is always reloaded. If these are avoided (e.g. architecture providing neither solution), it's visible in asm code that the variables are not reloaded. In this case, if a thread exists just between the moment the two values are read, the loop could spin forever. This patch adds the required _HA_ATOMIC_LOAD() on the relevant threads_enabled fields. It must be backported to 2.7.