| Message ID | 20230111131453.1626214-1-qiang1.zhang@intel.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | rcu: Fix the start_poll_synchronize_rcu_expedited() be invoked very early | expand |
On Wed, Jan 11, 2023 at 09:14:53PM +0800, Zqiang wrote: > Currently, the start_poll_synchronize_rcu_expedited() can be invoked > very early. before rcu_init(), the rcu_data structure's->mynode is not > initialized, if invoke start_poll_synchronize_rcu_expedited() before > rcu_init(), will access to NULL mynode pointer. > > This commit therefore add exp_seq_poll_rq member to rcu_state structure > to store snap seq number Is it even sane to poll that early in the morning? :-) > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> > --- > kernel/rcu/tree.c | 3 ++- > kernel/rcu/tree.h | 1 + > kernel/rcu/tree_exp.h | 6 ++++-- > 3 files changed, 7 insertions(+), 3 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 63545d79da51..34b13d6bd8c4 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -92,6 +92,7 @@ static struct rcu_state rcu_state = { > .exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex), > .exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex), > .ofl_lock = __ARCH_SPIN_LOCK_UNLOCKED, > + .exp_seq_poll_rq = RCU_GET_STATE_COMPLETED, I don't know if we really want to fix this, but assuming we do, can we rename it to boot_exp_seq_poll_rq? To avoid later confusion. Thanks.
On Wed, Jan 11, 2023 at 09:14:53PM +0800, Zqiang wrote: > Currently, the start_poll_synchronize_rcu_expedited() can be invoked > very early. before rcu_init(), the rcu_data structure's->mynode is not > initialized, if invoke start_poll_synchronize_rcu_expedited() before > rcu_init(), will access to NULL mynode pointer. > > This commit therefore add exp_seq_poll_rq member to rcu_state structure > to store snap seq number > >Is it even sane to poll that early in the morning? :-) According to d96c52fe4907c ("rcu: Add polled expedited grace-period primitives "), the start_poll_synchronize_rcu_expedited() can be invoked very early, that is to say can be invoked before rcu_init(), the following code snippet also shows that the start_poll_synchronize_rcu_expedited() may be called early. // Kick-start any polled grace periods that started early. if (!(per_cpu_ptr(&rcu_data, cpu)->mynode->exp_seq_poll_rq & 0x1)) (void)start_poll_synchronize_rcu_expedited(); But before rcu_init(), the rcu_data structure's->mynode is not initialized, so at least, we set rnp->exp_seq_poll_rq should be in case the rcu_init_invoked() returns true in start_poll_synchronize_rcu_expedited() . > > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> > --- > kernel/rcu/tree.c | 3 ++- > kernel/rcu/tree.h | 1 + > kernel/rcu/tree_exp.h | 6 ++++-- > 3 files changed, 7 insertions(+), 3 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 63545d79da51..34b13d6bd8c4 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -92,6 +92,7 @@ static struct rcu_state rcu_state = { > .exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex), > .exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex), > .ofl_lock = __ARCH_SPIN_LOCK_UNLOCKED, > + .exp_seq_poll_rq = RCU_GET_STATE_COMPLETED, > >I don't know if we really want to fix this, but assuming we do, >can we rename it to boot_exp_seq_poll_rq? To avoid later confusion. Will fix in next version. Thanks Zqiang > >Thanks.
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 63545d79da51..34b13d6bd8c4 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -92,6 +92,7 @@ static struct rcu_state rcu_state = { .exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex), .exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex), .ofl_lock = __ARCH_SPIN_LOCK_UNLOCKED, + .exp_seq_poll_rq = RCU_GET_STATE_COMPLETED, }; /* Dump rcu_node combining tree at boot to verify correct setup. */ @@ -4938,7 +4939,7 @@ void __init rcu_init(void) qovld_calc = qovld; // Kick-start any polled grace periods that started early. - if (!(per_cpu_ptr(&rcu_data, cpu)->mynode->exp_seq_poll_rq & 0x1)) + if (!(rcu_state.exp_seq_poll_rq & 0x1)) (void)start_poll_synchronize_rcu_expedited(); rcu_test_sync_prims(); diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 192536916f9a..dbc7c7484a7e 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -397,6 +397,7 @@ struct rcu_state { /* Synchronize offline with */ /* GP pre-initialization. */ int nocb_is_setup; /* nocb is setup from boot */ + unsigned long exp_seq_poll_rq; }; /* Values for rcu_state structure's gp_flags field. */ diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 956cd459ba7f..5964d1cccab1 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -1068,9 +1068,11 @@ unsigned long start_poll_synchronize_rcu_expedited(void) if (rcu_init_invoked()) raw_spin_lock_irqsave(&rnp->exp_poll_lock, flags); if (!poll_state_synchronize_rcu(s)) { - rnp->exp_seq_poll_rq = s; - if (rcu_init_invoked()) + if (rcu_init_invoked()) { + rnp->exp_seq_poll_rq = s; queue_work(rcu_gp_wq, &rnp->exp_poll_wq); + } else + rcu_state.exp_seq_poll_rq = s; } if (rcu_init_invoked()) raw_spin_unlock_irqrestore(&rnp->exp_poll_lock, flags);
Currently, the start_poll_synchronize_rcu_expedited() can be invoked very early. before rcu_init(), the rcu_data structure's->mynode is not initialized, if invoke start_poll_synchronize_rcu_expedited() before rcu_init(), will access to NULL mynode pointer. This commit therefore add exp_seq_poll_rq member to rcu_state structure to store snap seq number Signed-off-by: Zqiang <qiang1.zhang@intel.com> --- kernel/rcu/tree.c | 3 ++- kernel/rcu/tree.h | 1 + kernel/rcu/tree_exp.h | 6 ++++-- 3 files changed, 7 insertions(+), 3 deletions(-)