From: Mathieu Desnoyers Date: Sun, 17 Jan 2010 17:15:44 +0000 (-0500) Subject: Internal cleanup X-Git-Tag: v0.4.0~4 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=2dfb8b5e30bc2d268bcbc57eceb9c54d21b36d90;p=userspace-rcu.git Internal cleanup Signed-off-by: Mathieu Desnoyers --- diff --git a/urcu-bp.c b/urcu-bp.c index eda0005..fc6eedf 100644 --- a/urcu-bp.c +++ b/urcu-bp.c @@ -116,22 +116,29 @@ static void mutex_unlock(pthread_mutex_t *mutex) } } -/* - * called with rcu_gp_lock held. - */ -static void switch_next_rcu_qparity(void) -{ - STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); -} - -void wait_for_quiescent_state(void) +void update_counter_and_wait(void) { LIST_HEAD(qsreaders); int wait_loops = 0; struct rcu_reader *index, *tmp; - if (list_empty(®istry)) - return; + /* Switch parity: 1 -> 0, 0 -> 1 */ + STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); + + /* + * Must commit qparity update to memory before waiting for other parity + * quiescent state. Failure to do so could result in the writer waiting + * forever while new readers are always accessing data (no progress). + * Ensured by STORE_SHARED and LOAD_SHARED. + */ + + /* + * Adding a smp_mb() which is _not_ formally required, but makes the + * model easier to understand. It does not have a big performance impact + * anyway, given this is the write-side. + */ + smp_mb(); + /* * Wait for each thread rcu_reader.ctr count to become 0. */ @@ -167,44 +174,21 @@ void synchronize_rcu(void) mutex_lock(&rcu_gp_lock); - /* Remove old registry elements */ - rcu_gc_registry(); + if (list_empty(®istry)) + goto out; /* All threads should read qparity before accessing data structure - * where new ptr points to. Must be done within rcu_gp_lock because it - * iterates on reader threads.*/ + * where new ptr points to. */ /* Write new ptr before changing the qparity */ smp_mb(); - switch_next_rcu_qparity(); /* 0 -> 1 */ - - /* - * Must commit qparity update to memory before waiting for parity - * 0 quiescent state. Failure to do so could result in the writer - * waiting forever while new readers are always accessing data (no - * progress). - * Ensured by STORE_SHARED and LOAD_SHARED. - */ - - /* - * Adding a smp_mb() which is _not_ formally required, but makes the - * model easier to understand. It does not have a big performance impact - * anyway, given this is the write-side. - */ - smp_mb(); + /* Remove old registry elements */ + rcu_gc_registry(); /* * Wait for previous parity to be empty of readers. */ - wait_for_quiescent_state(); /* Wait readers in parity 0 */ - - /* - * Must finish waiting for quiescent state for parity 0 before - * committing qparity update to memory. Failure to do so could result in - * the writer waiting forever while new readers are always accessing - * data (no progress). - * Ensured by STORE_SHARED and LOAD_SHARED. - */ + update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */ /* * Adding a smp_mb() which is _not_ formally required, but makes the @@ -213,33 +197,17 @@ void synchronize_rcu(void) */ smp_mb(); - switch_next_rcu_qparity(); /* 1 -> 0 */ - /* - * Must commit qparity update to memory before waiting for parity - * 1 quiescent state. Failure to do so could result in the writer - * waiting forever while new readers are always accessing data (no - * progress). - * Ensured by STORE_SHARED and LOAD_SHARED. - */ - - /* - * Adding a smp_mb() which is _not_ formally required, but makes the - * model easier to understand. It does not have a big performance impact - * anyway, given this is the write-side. + * Wait for previous parity to be empty of readers. */ - smp_mb(); + update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */ /* - * Wait for previous parity to be empty of readers. + * Finish waiting for reader threads before letting the old ptr being + * freed. */ - wait_for_quiescent_state(); /* Wait readers in parity 1 */ - - /* Finish waiting for reader threads before letting the old ptr being - * freed. Must be done within rcu_gp_lock because it iterates on reader - * threads. */ smp_mb(); - +out: mutex_unlock(&rcu_gp_lock); ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); assert(!ret); diff --git a/urcu-qsbr.c b/urcu-qsbr.c index 1ac553f..155505a 100644 --- a/urcu-qsbr.c +++ b/urcu-qsbr.c @@ -106,14 +106,20 @@ static void wait_gp(void) NULL, NULL, 0); } -static void wait_for_quiescent_state(void) +static void update_counter_and_wait(void) { LIST_HEAD(qsreaders); int wait_loops = 0; struct rcu_reader *index, *tmp; - if (list_empty(®istry)) - return; +#if (BITS_PER_LONG < 64) + /* Switch parity: 1 -> 0, 0 -> 1 */ + STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR); +#else /* !(BITS_PER_LONG < 64) */ + /* Increment current G.P. */ + STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr + RCU_GP_CTR); +#endif /* !(BITS_PER_LONG < 64) */ + /* * Wait for each thread rcu_reader_qs_gp count to become 0. */ @@ -159,14 +165,6 @@ static void wait_for_quiescent_state(void) */ #if (BITS_PER_LONG < 64) -/* - * called with rcu_gp_lock held. - */ -static void switch_next_rcu_qparity(void) -{ - STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR); -} - void synchronize_rcu(void) { unsigned long was_online; @@ -189,20 +187,13 @@ void synchronize_rcu(void) mutex_lock(&rcu_gp_lock); - switch_next_rcu_qparity(); /* 0 -> 1 */ - - /* - * Must commit qparity update to memory before waiting for parity - * 0 quiescent state. Failure to do so could result in the writer - * waiting forever while new readers are always accessing data (no - * progress). - * Ensured by STORE_SHARED and LOAD_SHARED. - */ + if (list_empty(®istry)) + goto out; /* * Wait for previous parity to be empty of readers. */ - wait_for_quiescent_state(); /* Wait readers in parity 0 */ + update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */ /* * Must finish waiting for quiescent state for parity 0 before @@ -212,21 +203,18 @@ void synchronize_rcu(void) * Ensured by STORE_SHARED and LOAD_SHARED. */ - switch_next_rcu_qparity(); /* 1 -> 0 */ - /* - * Must commit qparity update to memory before waiting for parity - * 1 quiescent state. Failure to do so could result in the writer - * waiting forever while new readers are always accessing data (no - * progress). - * Ensured by STORE_SHARED and LOAD_SHARED. + * Adding a smp_mb() which is _not_ formally required, but makes the + * model easier to understand. It does not have a big performance impact + * anyway, given this is the write-side. */ + smp_mb(); /* * Wait for previous parity to be empty of readers. */ - wait_for_quiescent_state(); /* Wait readers in parity 1 */ - + update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */ +out: mutex_unlock(&rcu_gp_lock); /* @@ -254,8 +242,10 @@ void synchronize_rcu(void) STORE_SHARED(rcu_reader.ctr, 0); mutex_lock(&rcu_gp_lock); - STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr + RCU_GP_CTR); - wait_for_quiescent_state(); + if (list_empty(®istry)) + goto out; + update_counter_and_wait(); +out: mutex_unlock(&rcu_gp_lock); if (was_online) diff --git a/urcu.c b/urcu.c index 6e95891..e93170d 100644 --- a/urcu.c +++ b/urcu.c @@ -120,14 +120,6 @@ static void mutex_unlock(pthread_mutex_t *mutex) } } -/* - * called with rcu_gp_lock held. - */ -static void switch_next_rcu_qparity(void) -{ - STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); -} - #ifdef RCU_MEMBARRIER static void smp_mb_heavy(void) { @@ -207,14 +199,29 @@ static void wait_gp(void) NULL, NULL, 0); } -void wait_for_quiescent_state(void) +void update_counter_and_wait(void) { LIST_HEAD(qsreaders); int wait_loops = 0; struct rcu_reader *index, *tmp; - if (list_empty(®istry)) - return; + /* Switch parity: 1 -> 0, 0 -> 1 */ + STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); + + /* + * Must commit qparity update to memory before waiting for other parity + * quiescent state. Failure to do so could result in the writer waiting + * forever while new readers are always accessing data (no progress). + * Ensured by STORE_SHARED and LOAD_SHARED. + */ + + /* + * Adding a smp_mb() which is _not_ formally required, but makes the + * model easier to understand. It does not have a big performance impact + * anyway, given this is the write-side. + */ + smp_mb(); + /* * Wait for each thread rcu_reader.ctr count to become 0. */ @@ -280,33 +287,19 @@ void synchronize_rcu(void) { mutex_lock(&rcu_gp_lock); + if (list_empty(®istry)) + goto out; + /* All threads should read qparity before accessing data structure * where new ptr points to. Must be done within rcu_gp_lock because it * iterates on reader threads.*/ /* Write new ptr before changing the qparity */ smp_mb_heavy(); - switch_next_rcu_qparity(); /* 0 -> 1 */ - - /* - * Must commit qparity update to memory before waiting for parity - * 0 quiescent state. Failure to do so could result in the writer - * waiting forever while new readers are always accessing data (no - * progress). - * Ensured by STORE_SHARED and LOAD_SHARED. - */ - - /* - * Adding a smp_mb() which is _not_ formally required, but makes the - * model easier to understand. It does not have a big performance impact - * anyway, given this is the write-side. - */ - smp_mb(); - /* * Wait for previous parity to be empty of readers. */ - wait_for_quiescent_state(); /* Wait readers in parity 0 */ + update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */ /* * Must finish waiting for quiescent state for parity 0 before @@ -323,33 +316,16 @@ void synchronize_rcu(void) */ smp_mb(); - switch_next_rcu_qparity(); /* 1 -> 0 */ - - /* - * Must commit qparity update to memory before waiting for parity - * 1 quiescent state. Failure to do so could result in the writer - * waiting forever while new readers are always accessing data (no - * progress). - * Ensured by STORE_SHARED and LOAD_SHARED. - */ - - /* - * Adding a smp_mb() which is _not_ formally required, but makes the - * model easier to understand. It does not have a big performance impact - * anyway, given this is the write-side. - */ - smp_mb(); - /* * Wait for previous parity to be empty of readers. */ - wait_for_quiescent_state(); /* Wait readers in parity 1 */ + update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */ /* Finish waiting for reader threads before letting the old ptr being * freed. Must be done within rcu_gp_lock because it iterates on reader * threads. */ smp_mb_heavy(); - +out: mutex_unlock(&rcu_gp_lock); }