Sorry for the fragment, but I am just aware of this and think it is
better to fold into the same series.
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
>
