On Mon, Nov 28, 2022 at 10:01:08PM +0800, Pingfan Liu wrote: > On Mon, Nov 28, 2022 at 08:40:22AM +0000, Zhang, Qiang1 wrote: > > >The state SRCU_SIZE_WAIT_CALL is only used in srcu_gp_start_if_needed(). > > >And it is not needed. Because counter_wrap_check has guarantee that both > > >srcu_gp_seq_needed and srcu_gp_seq_needed_exp are not far behind > > >srcu_gp_seq and no false alarm will be raised by the statement in > > >srcu_gp_start_if_needed() > > > > > > ULONG_CMP_LT(sdp->srcu_gp_seq_needed, s) > > > > > >As a result, once if SRCU_SIZE_WAIT_BARRIER is seen, the tree snp can be > > >used immediately, not need to wait for another srcu_gp_end() to update > > >the srcu_gp_seq_needed and srcu_gp_seq_needed_exp to avoid false alarm. > > > > > >Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx> > > >Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx> > > >Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx> > > >Cc: Frederic Weisbecker <frederic@xxxxxxxxxx> > > >Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx> > > >Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> > > >Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> > > >Cc: "Zhang, Qiang1" <qiang1.zhang@xxxxxxxxx> > > >To: rcu@xxxxxxxxxxxxxxx > > >--- > > > kernel/rcu/srcutree.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > >diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c > > >index 1c304fec89c0..fe0759d89c2d 100644 > > >--- a/kernel/rcu/srcutree.c > > >+++ b/kernel/rcu/srcutree.c > > >@@ -1092,7 +1092,7 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp, > > > check_init_srcu_struct(ssp); > > > idx = srcu_read_lock(ssp); > > > ss_state = smp_load_acquire(&ssp->srcu_size_state); > > >- if (ss_state < SRCU_SIZE_WAIT_CALL) > > >+ if (ss_state < SRCU_SIZE_WAIT_BARRIER) > > > sdp = per_cpu_ptr(ssp->sda, 0); > > > > Hi Pingfan > > > > should it be used get_boot_cpu_id() ? > > I am not sure which branch to work on. For RCU patches, the "dev" branch of the -rcu tree. For more information, please see: https://mirrors.edge.kernel.org/pub/linux/kernel/people/paulmck/rcutodo.html Thanx, Paul > Thanks, > > Pingfan > > > Thanks > > Zqiang > > > > > else > > > sdp = raw_cpu_ptr(ssp->sda); > > >-- > > >2.31.1 > > >
