| Message ID | 20221120152040.7460-1-kernelfans@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | srcu: Eliminate the case that snp_seq bigger than snap in srcu_funnel_gp_start() | expand |
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@gmail.com> 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@gmail.com>
> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
> Cc: "Paul E. McKenney" <paulmck@kernel.org>
> Cc: Frederic Weisbecker <frederic@kernel.org>
> Cc: Josh Triplett <josh@joshtriplett.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> To: rcu@vger.kernel.org
> ---
> 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
>
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@gmail.com> 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@gmail.com> > > Cc: Lai Jiangshan <jiangshanlai@gmail.com> > > Cc: "Paul E. McKenney" <paulmck@kernel.org> > > Cc: Frederic Weisbecker <frederic@kernel.org> > > Cc: Josh Triplett <josh@joshtriplett.org> > > Cc: Steven Rostedt <rostedt@goodmis.org> > > Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> > > To: rcu@vger.kernel.org > > --- > > 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 > >
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;
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@gmail.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Frederic Weisbecker <frederic@kernel.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> To: rcu@vger.kernel.org --- include/linux/rcupdate.h | 1 + kernel/rcu/srcutree.c | 10 +++++----- 2 files changed, 6 insertions(+), 5 deletions(-)