forked from luck/tmp_suning_uos_patched
dfeb9765ce
The current approach to RCU priority boosting uses an rt_mutex strictly for its priority-boosting side effects. The rt_mutex_init_proxy_locked() function is used by the booster to initialize the lock as held by the boostee. The booster then uses rt_mutex_lock() to acquire this rt_mutex, which priority-boosts the boostee. When the boostee reaches the end of its outermost RCU read-side critical section, it checks a field in its task structure to see whether it has been boosted, and, if so, uses rt_mutex_unlock() to release the rt_mutex. The booster can then go on to boost the next task that is blocking the current RCU grace period. But reasonable implementations of rt_mutex_unlock() might result in the boostee referencing the rt_mutex's data after releasing it. But the booster might have re-initialized the rt_mutex between the time that the boostee released it and the time that it later referenced it. This is clearly asking for trouble, so this commit introduces a completion that forces the booster to wait until the boostee has completely finished with the rt_mutex, thus avoiding the case where the booster is re-initializing the rt_mutex before the last boostee's last reference to that rt_mutex. This of course does introduce some overhead, but the priority-boosting code paths are miles from any possible fastpath, and the overhead of executing the completion will normally be quite small compared to the overhead of priority boosting and deboosting, so this should be OK. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
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| .. | ||
| Makefile | ||
| rcu.h | ||
| rcutorture.c | ||
| srcu.c | ||
| tiny_plugin.h | ||
| tiny.c | ||
| tree_plugin.h | ||
| tree_trace.c | ||
| tree.c | ||
| tree.h | ||
| update.c | ||