On Sun, Nov 20, 2022 at 11:23:46PM +0800, Pingfan Liu wrote:
> Sorry for the fragment, but I am just aware of this and think it is
> better to fold into the same series.
Very well, I look forward to seeing the new version of this series.
Thanx, Paul
> Thanks,
>
> Pingfan
>
> On Sun, Nov 20, 2022 at 11:20 PM Pingfan Liu <kernelfans@xxxxxxxxx> wrote:
> >
> > Since the srcu read lock is still held during srcu_funnel_gp_start(),
> > the seq snap should be the largest number for the slot
> > srcu_have_cbs[idx].
> >
> > 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>
> > To: rcu@xxxxxxxxxxxxxxx
> > ---
> > include/linux/rcupdate.h | 1 +
> > kernel/rcu/srcutree.c | 10 +++++-----
> > 2 files changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > index 08605ce7379d..a09007236660 100644
> > --- a/include/linux/rcupdate.h
> > +++ b/include/linux/rcupdate.h
> > @@ -32,6 +32,7 @@
> > #include <linux/context_tracking_irq.h>
> >
> > #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b))
> > +#define ULONG_CMP_GT(a, b) (ULONG_MAX / 2 > (a) - (b))
> > #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b))
> > #define ulong2long(a) (*(long *)(&(a)))
> > #define USHORT_CMP_GE(a, b) (USHRT_MAX / 2 >= (unsigned short)((a) - (b)))
> > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> > index c54d6c04751f..057752db1125 100644
> > --- a/kernel/rcu/srcutree.c
> > +++ b/kernel/rcu/srcutree.c
> > @@ -900,14 +900,14 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp,
> > for (snp = snp_leaf; snp != NULL; snp = snp->srcu_parent) {
> > spin_lock_irqsave_rcu_node(snp, flags);
> > snp_seq = snp->srcu_have_cbs[idx];
> > - if (!srcu_invl_snp_seq(snp_seq) && ULONG_CMP_GE(snp_seq, s)) {
> > + /* s should be the biggest in the current slot. Hence only LE is
> > + * valid
> > + */
> > + BUG_ON(ULONG_CMP_GT(snp_seq, s));
> > + if (!srcu_invl_snp_seq(snp_seq) && (snp_seq == s)) {
> > if (snp == snp_leaf && snp_seq == s)
> > snp->srcu_data_have_cbs[idx] |= sdp->grpmask;
> > spin_unlock_irqrestore_rcu_node(snp, flags);
> > - if (snp == snp_leaf && snp_seq != s) {
> > - srcu_schedule_cbs_sdp(sdp, do_norm ? SRCU_INTERVAL : 0);
> > - return;
> > - }
> > if (!do_norm)
> > srcu_funnel_exp_start(ssp, snp, s);
> > return;
> > --
> > 2.31.1
> >
