diff options
Diffstat (limited to 'qemu/util/rcu.c')
| -rw-r--r-- | qemu/util/rcu.c | 54 |
1 files changed, 36 insertions, 18 deletions
diff --git a/qemu/util/rcu.c b/qemu/util/rcu.c index cdcad678b..bceb3e472 100644 --- a/qemu/util/rcu.c +++ b/qemu/util/rcu.c @@ -26,12 +26,8 @@ * IBM's contributions to this file may be relicensed under LGPLv2 or later. */ +#include "qemu/osdep.h" #include "qemu-common.h" -#include <stdio.h> -#include <assert.h> -#include <stdlib.h> -#include <stdint.h> -#include <errno.h> #include "qemu/rcu.h" #include "qemu/atomic.h" #include "qemu/thread.h" @@ -47,7 +43,8 @@ unsigned long rcu_gp_ctr = RCU_GP_LOCKED; QemuEvent rcu_gp_event; -static QemuMutex rcu_gp_lock; +static QemuMutex rcu_registry_lock; +static QemuMutex rcu_sync_lock; /* * Check whether a quiescent state was crossed between the beginning of @@ -66,7 +63,7 @@ static inline int rcu_gp_ongoing(unsigned long *ctr) */ __thread struct rcu_reader_data rcu_reader; -/* Protected by rcu_gp_lock. */ +/* Protected by rcu_registry_lock. */ typedef QLIST_HEAD(, rcu_reader_data) ThreadList; static ThreadList registry = QLIST_HEAD_INITIALIZER(registry); @@ -114,10 +111,26 @@ static void wait_for_readers(void) break; } - /* Wait for one thread to report a quiescent state and - * try again. + /* Wait for one thread to report a quiescent state and try again. + * Release rcu_registry_lock, so rcu_(un)register_thread() doesn't + * wait too much time. + * + * rcu_register_thread() may add nodes to ®istry; it will not + * wake up synchronize_rcu, but that is okay because at least another + * thread must exit its RCU read-side critical section before + * synchronize_rcu is done. The next iteration of the loop will + * move the new thread's rcu_reader from ®istry to &qsreaders, + * because rcu_gp_ongoing() will return false. + * + * rcu_unregister_thread() may remove nodes from &qsreaders instead + * of ®istry if it runs during qemu_event_wait. That's okay; + * the node then will not be added back to ®istry by QLIST_SWAP + * below. The invariant is that the node is part of one list when + * rcu_registry_lock is released. */ + qemu_mutex_unlock(&rcu_registry_lock); qemu_event_wait(&rcu_gp_event); + qemu_mutex_lock(&rcu_registry_lock); } /* put back the reader list in the registry */ @@ -126,7 +139,8 @@ static void wait_for_readers(void) void synchronize_rcu(void) { - qemu_mutex_lock(&rcu_gp_lock); + qemu_mutex_lock(&rcu_sync_lock); + qemu_mutex_lock(&rcu_registry_lock); if (!QLIST_EMPTY(®istry)) { /* In either case, the atomic_mb_set below blocks stores that free @@ -149,7 +163,8 @@ void synchronize_rcu(void) wait_for_readers(); } - qemu_mutex_unlock(&rcu_gp_lock); + qemu_mutex_unlock(&rcu_registry_lock); + qemu_mutex_unlock(&rcu_sync_lock); } @@ -273,23 +288,24 @@ void call_rcu1(struct rcu_head *node, void (*func)(struct rcu_head *node)) void rcu_register_thread(void) { assert(rcu_reader.ctr == 0); - qemu_mutex_lock(&rcu_gp_lock); + qemu_mutex_lock(&rcu_registry_lock); QLIST_INSERT_HEAD(®istry, &rcu_reader, node); - qemu_mutex_unlock(&rcu_gp_lock); + qemu_mutex_unlock(&rcu_registry_lock); } void rcu_unregister_thread(void) { - qemu_mutex_lock(&rcu_gp_lock); + qemu_mutex_lock(&rcu_registry_lock); QLIST_REMOVE(&rcu_reader, node); - qemu_mutex_unlock(&rcu_gp_lock); + qemu_mutex_unlock(&rcu_registry_lock); } static void rcu_init_complete(void) { QemuThread thread; - qemu_mutex_init(&rcu_gp_lock); + qemu_mutex_init(&rcu_registry_lock); + qemu_mutex_init(&rcu_sync_lock); qemu_event_init(&rcu_gp_event, true); qemu_event_init(&rcu_call_ready_event, false); @@ -306,12 +322,14 @@ static void rcu_init_complete(void) #ifdef CONFIG_POSIX static void rcu_init_lock(void) { - qemu_mutex_lock(&rcu_gp_lock); + qemu_mutex_lock(&rcu_sync_lock); + qemu_mutex_lock(&rcu_registry_lock); } static void rcu_init_unlock(void) { - qemu_mutex_unlock(&rcu_gp_lock); + qemu_mutex_unlock(&rcu_registry_lock); + qemu_mutex_unlock(&rcu_sync_lock); } #endif |