* [PATCH 6.12.y 0/3] backport missing dependencies of d66792919d4f
@ 2026-05-22 21:31 Lukas Beckmann
2026-05-22 21:31 ` [PATCH 6.12.y 1/3] sched/deadline: Less agressive dl_server handling Lukas Beckmann
` (3 more replies)
0 siblings, 4 replies; 6+ messages in thread
From: Lukas Beckmann @ 2026-05-22 21:31 UTC (permalink / raw)
To: Sasha Levin
Cc: stable, regressions, Mike Galbraith, Peter Zijlstra, Juri Lelli
Commit d66792919d4f ("sched/deadline: Use revised wakeup rule for
dl_server") in the 6.12.y stable tree (upstream commit 14a857056466)
depends on three upstream commits that were not backported:
commit cccb45d7c429 ("sched/deadline: Less agressive dl_server handling")
commit 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
commit a3a70caf7906 ("sched/deadline: Fix dl_server behaviour")
Without these, cyclictest under load reports latencies up to ~50ms on
PREEMPT_RT.
For context, see the regression report:
https://lore.kernel.org/regressions/04657838-46d1-432d-95e1-eb73b930b032@mailbox.org
Testing:
Tested on two different machines with Debian's PREEMPT_RT config for about
10 hours.
Without these patches cyclictest under load spikes to ~50ms in less than
30 minutes, with the series applied the latency spikes are gone.
Thanks,
Lukas
Peter Zijlstra (3):
sched/deadline: Less agressive dl_server handling
sched/deadline: Fix dl_server getting stuck
sched/deadline: Fix dl_server behaviour
include/linux/sched.h | 1 -
kernel/sched/deadline.c | 16 +++-------------
kernel/sched/fair.c | 16 +---------------
kernel/sched/sched.h | 37 +++++++++++++++++++++++++++++++------
4 files changed, 35 insertions(+), 35 deletions(-)
--
2.54.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 6.12.y 1/3] sched/deadline: Less agressive dl_server handling
2026-05-22 21:31 [PATCH 6.12.y 0/3] backport missing dependencies of d66792919d4f Lukas Beckmann
@ 2026-05-22 21:31 ` Lukas Beckmann
2026-05-22 21:31 ` [PATCH 6.12.y 2/3] sched/deadline: Fix dl_server getting stuck Lukas Beckmann
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Lukas Beckmann @ 2026-05-22 21:31 UTC (permalink / raw)
To: Sasha Levin
Cc: stable, regressions, Mike Galbraith, Peter Zijlstra, Juri Lelli
From: Peter Zijlstra <peterz@infradead.org>
commit cccb45d7c4295bbfeba616582d0249f2d21e6df5 upstream.
Chris reported that commit 5f6bd380c7bd ("sched/rt: Remove default
bandwidth control") caused a significant dip in his favourite
benchmark of the day. Simply disabling dl_server cured things.
His workload hammers the 0->1, 1->0 transitions, and the
dl_server_{start,stop}() overhead kills it -- fairly obviously a bad
idea in hind sight and all that.
Change things around to only disable the dl_server when there has not
been a fair task around for a whole period. Since the default period
is 1 second, this ensures the benchmark never trips this, overhead
gone.
Fixes: 557a6bfc662c ("sched/fair: Add trivial fair server")
Reported-by: Chris Mason <clm@meta.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20250702121158.465086194@infradead.org
[ adjust context for renamed/removed variable names ]
Signed-off-by: Lukas Beckmann <lbckmnn@mailbox.org>
---
include/linux/sched.h | 1 +
kernel/sched/deadline.c | 25 ++++++++++++++++++++++---
kernel/sched/fair.c | 9 ---------
3 files changed, 23 insertions(+), 12 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2e4c437c7c90..299a65a92d2e 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -674,6 +674,7 @@ struct sched_dl_entity {
unsigned int dl_defer : 1;
unsigned int dl_defer_armed : 1;
unsigned int dl_defer_running : 1;
+ unsigned int dl_server_idle : 1;
/*
* Bandwidth enforcement timer. Each -deadline task has its
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 1ef891f8e3f2..9c5fa95b345a 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1201,6 +1201,8 @@ static void __push_dl_task(struct rq *rq, struct rq_flags *rf)
/* a defer timer will not be reset if the runtime consumed was < dl_server_min_res */
static const u64 dl_server_min_res = 1 * NSEC_PER_MSEC;
+static bool dl_server_stopped(struct sched_dl_entity *dl_se);
+
static enum hrtimer_restart dl_server_timer(struct hrtimer *timer, struct sched_dl_entity *dl_se)
{
struct rq *rq = rq_of_dl_se(dl_se);
@@ -1220,6 +1222,7 @@ static enum hrtimer_restart dl_server_timer(struct hrtimer *timer, struct sched_
if (!dl_se->server_has_tasks(dl_se)) {
replenish_dl_entity(dl_se);
+ dl_server_stopped(dl_se);
return HRTIMER_NORESTART;
}
@@ -1626,8 +1629,10 @@ void dl_server_update_idle_time(struct rq *rq, struct task_struct *p)
void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec)
{
/* 0 runtime = fair server disabled */
- if (dl_se->dl_runtime)
+ if (dl_se->dl_runtime) {
+ dl_se->dl_server_idle = 0;
update_curr_dl_se(dl_se->rq, dl_se, delta_exec);
+ }
}
/*
@@ -1850,7 +1855,7 @@ void dl_server_start(struct sched_dl_entity *dl_se)
setup_new_dl_entity(dl_se);
}
- if (!dl_se->dl_runtime)
+ if (!dl_se->dl_runtime || dl_se->dl_server_active)
return;
dl_se->dl_server_active = 1;
@@ -1871,6 +1876,20 @@ void dl_server_stop(struct sched_dl_entity *dl_se)
dl_se->dl_server_active = 0;
}
+static bool dl_server_stopped(struct sched_dl_entity *dl_se)
+{
+ if (!dl_se->dl_server_active)
+ return false;
+
+ if (dl_se->dl_server_idle) {
+ dl_server_stop(dl_se);
+ return true;
+ }
+
+ dl_se->dl_server_idle = 1;
+ return false;
+}
+
void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq,
dl_server_has_tasks_f has_tasks,
dl_server_pick_f pick_task)
@@ -2628,7 +2647,7 @@ static struct task_struct *__pick_task_dl(struct rq *rq)
if (dl_server(dl_se)) {
p = dl_se->server_pick_task(dl_se);
if (!p) {
- if (dl_server_active(dl_se)) {
+ if (!dl_server_stopped(dl_se)) {
dl_se->dl_yielded = 1;
update_curr_dl_se(rq, dl_se, 0);
}
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a0a47e50b71c..d26e078d0623 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5972,7 +5972,6 @@ static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
struct sched_entity *se;
long queued_delta, runnable_delta, idle_task_delta, delayed_delta, dequeue = 1;
- long rq_h_nr_queued = rq->cfs.h_nr_queued;
raw_spin_lock(&cfs_b->lock);
/* This will start the period timer if necessary */
@@ -6059,10 +6058,6 @@ static bool throttle_cfs_rq(struct cfs_rq *cfs_rq)
/* At this point se is NULL and we are at root level*/
sub_nr_running(rq, queued_delta);
-
- /* Stop the fair server if throttling resulted in no runnable tasks */
- if (rq_h_nr_queued && !rq->cfs.h_nr_queued)
- dl_server_stop(&rq->fair_server);
done:
/*
* Note: distribution will already see us throttled via the
@@ -7162,7 +7157,6 @@ static void set_next_buddy(struct sched_entity *se);
static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags)
{
bool was_sched_idle = sched_idle_rq(rq);
- int rq_h_nr_queued = rq->cfs.h_nr_queued;
bool task_sleep = flags & DEQUEUE_SLEEP;
bool task_delayed = flags & DEQUEUE_DELAYED;
struct task_struct *p = NULL;
@@ -7251,9 +7245,6 @@ static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags)
sub_nr_running(rq, h_nr_queued);
- if (rq_h_nr_queued && !rq->cfs.h_nr_queued)
- dl_server_stop(&rq->fair_server);
-
/* balance early to pull high priority tasks */
if (unlikely(!was_sched_idle && sched_idle_rq(rq)))
rq->next_balance = jiffies;
--
2.54.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 6.12.y 2/3] sched/deadline: Fix dl_server getting stuck
2026-05-22 21:31 [PATCH 6.12.y 0/3] backport missing dependencies of d66792919d4f Lukas Beckmann
2026-05-22 21:31 ` [PATCH 6.12.y 1/3] sched/deadline: Less agressive dl_server handling Lukas Beckmann
@ 2026-05-22 21:31 ` Lukas Beckmann
2026-05-22 21:31 ` [PATCH 6.12.y 3/3] sched/deadline: Fix dl_server behaviour Lukas Beckmann
2026-05-24 12:09 ` [PATCH 6.12.y 0/3] backport missing dependencies of d66792919d4f Sasha Levin
3 siblings, 0 replies; 6+ messages in thread
From: Lukas Beckmann @ 2026-05-22 21:31 UTC (permalink / raw)
To: Sasha Levin
Cc: stable, regressions, Mike Galbraith, Peter Zijlstra, Juri Lelli
From: Peter Zijlstra <peterz@infradead.org>
commit 4ae8d9aa9f9dc7137ea5e564d79c5aa5af1bc45c upstream.
John found it was easy to hit lockup warnings when running locktorture
on a 2 CPU VM, which he bisected down to: commit cccb45d7c429
("sched/deadline: Less agressive dl_server handling").
While debugging it seems there is a chance where we end up with the
dl_server dequeued, with dl_se->dl_server_active. This causes
dl_server_start() to return without enqueueing the dl_server, thus it
fails to run when RT tasks starve the cpu.
When this happens, dl_server_timer() catches the
'!dl_se->server_has_tasks(dl_se)' case, which then calls
replenish_dl_entity() and dl_server_stopped() and finally return
HRTIMER_NO_RESTART.
This ends in no new timer and also no enqueue, leaving the dl_server
'dead', allowing starvation.
What should have happened is for the bandwidth timer to start the
zero-laxity timer, which in turn would enqueue the dl_server and cause
dl_se->server_pick_task() to be called -- which will stop the
dl_server if no fair tasks are observed for a whole period.
IOW, it is totally irrelevant if there are fair tasks at the moment of
bandwidth refresh.
This removes all dl_se->server_has_tasks() users, so remove the whole
thing.
Fixes: cccb45d7c4295 ("sched/deadline: Less agressive dl_server handling")
Reported-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: John Stultz <jstultz@google.com>
[ adjust renamed variable in fair_server_has_tasks (which this patch
removes) ]
Signed-off-by: Lukas Beckmann <lbckmnn@mailbox.org>
---
include/linux/sched.h | 1 -
kernel/sched/deadline.c | 12 +-----------
kernel/sched/fair.c | 7 +------
kernel/sched/sched.h | 4 ----
4 files changed, 2 insertions(+), 22 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 299a65a92d2e..464d281aa2e4 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -701,7 +701,6 @@ struct sched_dl_entity {
* runnable task.
*/
struct rq *rq;
- dl_server_has_tasks_f server_has_tasks;
dl_server_pick_f server_pick_task;
#ifdef CONFIG_RT_MUTEXES
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 9c5fa95b345a..7a2ea2183975 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -916,7 +916,7 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
*/
if (dl_se->dl_defer && !dl_se->dl_defer_running &&
dl_time_before(rq_clock(dl_se->rq), dl_se->deadline - dl_se->runtime)) {
- if (!is_dl_boosted(dl_se) && dl_se->server_has_tasks(dl_se)) {
+ if (!is_dl_boosted(dl_se)) {
/*
* Set dl_se->dl_defer_armed and dl_throttled variables to
@@ -1201,8 +1201,6 @@ static void __push_dl_task(struct rq *rq, struct rq_flags *rf)
/* a defer timer will not be reset if the runtime consumed was < dl_server_min_res */
static const u64 dl_server_min_res = 1 * NSEC_PER_MSEC;
-static bool dl_server_stopped(struct sched_dl_entity *dl_se);
-
static enum hrtimer_restart dl_server_timer(struct hrtimer *timer, struct sched_dl_entity *dl_se)
{
struct rq *rq = rq_of_dl_se(dl_se);
@@ -1220,12 +1218,6 @@ static enum hrtimer_restart dl_server_timer(struct hrtimer *timer, struct sched_
if (!dl_se->dl_runtime)
return HRTIMER_NORESTART;
- if (!dl_se->server_has_tasks(dl_se)) {
- replenish_dl_entity(dl_se);
- dl_server_stopped(dl_se);
- return HRTIMER_NORESTART;
- }
-
if (dl_se->dl_defer_armed) {
/*
* First check if the server could consume runtime in background.
@@ -1891,11 +1883,9 @@ static bool dl_server_stopped(struct sched_dl_entity *dl_se)
}
void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq,
- dl_server_has_tasks_f has_tasks,
dl_server_pick_f pick_task)
{
dl_se->rq = rq;
- dl_se->server_has_tasks = has_tasks;
dl_se->server_pick_task = pick_task;
}
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d26e078d0623..f36512892adf 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9058,11 +9058,6 @@ static struct task_struct *__pick_next_task_fair(struct rq *rq, struct task_stru
return pick_next_task_fair(rq, prev, NULL);
}
-static bool fair_server_has_tasks(struct sched_dl_entity *dl_se)
-{
- return !!dl_se->rq->cfs.nr_running;
-}
-
static struct task_struct *fair_server_pick_task(struct sched_dl_entity *dl_se)
{
return pick_task_fair(dl_se->rq);
@@ -9074,7 +9069,7 @@ void fair_server_init(struct rq *rq)
init_dl_entity(dl_se);
- dl_server_init(dl_se, rq, fair_server_has_tasks, fair_server_pick_task);
+ dl_server_init(dl_se, rq, fair_server_pick_task);
}
/*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index a09e2d25edd5..9391ff62cdaa 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -371,9 +371,6 @@ extern s64 dl_scaled_delta_exec(struct rq *rq, struct sched_dl_entity *dl_se, s6
*
* dl_se::rq -- runqueue we belong to.
*
- * dl_se::server_has_tasks() -- used on bandwidth enforcement; we 'stop' the
- * server when it runs out of tasks to run.
- *
* dl_se::server_pick() -- nested pick_next_task(); we yield the period if this
* returns NULL.
*
@@ -389,7 +386,6 @@ extern void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec);
extern void dl_server_start(struct sched_dl_entity *dl_se);
extern void dl_server_stop(struct sched_dl_entity *dl_se);
extern void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq,
- dl_server_has_tasks_f has_tasks,
dl_server_pick_f pick_task);
extern void dl_server_update_idle_time(struct rq *rq,
--
2.54.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 6.12.y 3/3] sched/deadline: Fix dl_server behaviour
2026-05-22 21:31 [PATCH 6.12.y 0/3] backport missing dependencies of d66792919d4f Lukas Beckmann
2026-05-22 21:31 ` [PATCH 6.12.y 1/3] sched/deadline: Less agressive dl_server handling Lukas Beckmann
2026-05-22 21:31 ` [PATCH 6.12.y 2/3] sched/deadline: Fix dl_server getting stuck Lukas Beckmann
@ 2026-05-22 21:31 ` Lukas Beckmann
2026-05-24 12:09 ` [PATCH 6.12.y 0/3] backport missing dependencies of d66792919d4f Sasha Levin
3 siblings, 0 replies; 6+ messages in thread
From: Lukas Beckmann @ 2026-05-22 21:31 UTC (permalink / raw)
To: Sasha Levin
Cc: stable, regressions, Mike Galbraith, Peter Zijlstra, Juri Lelli
From: Peter Zijlstra <peterz@infradead.org>
commit a3a70caf7906708bf9bbc80018752a6b36543808 upstream.
John reported undesirable behaviour with the dl_server since commit:
cccb45d7c4295 ("sched/deadline: Less agressive dl_server handling").
When starving fair tasks on purpose (starting spinning FIFO tasks),
his fair workload, which often goes (briefly) idle, would delay fair
invocations for a second, running one invocation per second was both
unexpected and terribly slow.
The reason this happens is that when dl_se->server_pick_task() returns
NULL, indicating no runnable tasks, it would yield, pushing any later
jobs out a whole period (1 second).
Instead simply stop the server. This should restore behaviour in that
a later wakeup (which restarts the server) will be able to continue
running (subject to the CBS wakeup rules).
Notably, this does not re-introduce the behaviour cccb45d7c4295 set
out to solve, any start/stop cycle is naturally throttled by the timer
period (no active cancel).
Fixes: cccb45d7c4295 ("sched/deadline: Less agressive dl_server handling")
Reported-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: John Stultz <jstultz@google.com>
[ adjust dl_server_stopped (which this patch removes) ]
Closes: https://lore.kernel.org/regressions/04657838-46d1-432d-95e1-eb73b930b032@mailbox.org
Signed-off-by: Lukas Beckmann <lbckmnn@mailbox.org>
---
include/linux/sched.h | 1 -
kernel/sched/deadline.c | 23 ++---------------------
kernel/sched/sched.h | 33 +++++++++++++++++++++++++++++++--
3 files changed, 33 insertions(+), 24 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 464d281aa2e4..f9ffe42cae17 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -674,7 +674,6 @@ struct sched_dl_entity {
unsigned int dl_defer : 1;
unsigned int dl_defer_armed : 1;
unsigned int dl_defer_running : 1;
- unsigned int dl_server_idle : 1;
/*
* Bandwidth enforcement timer. Each -deadline task has its
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 7a2ea2183975..a6c699e43111 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1621,10 +1621,8 @@ void dl_server_update_idle_time(struct rq *rq, struct task_struct *p)
void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec)
{
/* 0 runtime = fair server disabled */
- if (dl_se->dl_runtime) {
- dl_se->dl_server_idle = 0;
+ if (dl_se->dl_runtime)
update_curr_dl_se(dl_se->rq, dl_se, delta_exec);
- }
}
/*
@@ -1868,20 +1866,6 @@ void dl_server_stop(struct sched_dl_entity *dl_se)
dl_se->dl_server_active = 0;
}
-static bool dl_server_stopped(struct sched_dl_entity *dl_se)
-{
- if (!dl_se->dl_server_active)
- return false;
-
- if (dl_se->dl_server_idle) {
- dl_server_stop(dl_se);
- return true;
- }
-
- dl_se->dl_server_idle = 1;
- return false;
-}
-
void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq,
dl_server_pick_f pick_task)
{
@@ -2637,10 +2621,7 @@ static struct task_struct *__pick_task_dl(struct rq *rq)
if (dl_server(dl_se)) {
p = dl_se->server_pick_task(dl_se);
if (!p) {
- if (!dl_server_stopped(dl_se)) {
- dl_se->dl_yielded = 1;
- update_curr_dl_se(rq, dl_se, 0);
- }
+ dl_server_stop(dl_se);
goto again;
}
rq->dl_server = dl_se;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 9391ff62cdaa..7956abeb9154 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -377,10 +377,39 @@ extern s64 dl_scaled_delta_exec(struct rq *rq, struct sched_dl_entity *dl_se, s6
* dl_server_update() -- called from update_curr_common(), propagates runtime
* to the server.
*
- * dl_server_start()
- * dl_server_stop() -- start/stop the server when it has (no) tasks.
+ * dl_server_start() -- start the server when it has tasks; it will stop
+ * automatically when there are no more tasks, per
+ * dl_se::server_pick() returning NULL.
+ *
+ * dl_server_stop() -- (force) stop the server; use when updating
+ * parameters.
*
* dl_server_init() -- initializes the server.
+ *
+ * When started the dl_server will (per dl_defer) schedule a timer for its
+ * zero-laxity point -- that is, unlike regular EDF tasks which run ASAP, a
+ * server will run at the very end of its period.
+ *
+ * This is done such that any runtime from the target class can be accounted
+ * against the server -- through dl_server_update() above -- such that when it
+ * becomes time to run, it might already be out of runtime and get deferred
+ * until the next period. In this case dl_server_timer() will alternate
+ * between defer and replenish but never actually enqueue the server.
+ *
+ * Only when the target class does not manage to exhaust the server's runtime
+ * (there's actualy starvation in the given period), will the dl_server get on
+ * the runqueue. Once queued it will pick tasks from the target class and run
+ * them until either its runtime is exhaused, at which point its back to
+ * dl_server_timer, or until there are no more tasks to run, at which point
+ * the dl_server stops itself.
+ *
+ * By stopping at this point the dl_server retains bandwidth, which, if a new
+ * task wakes up imminently (starting the server again), can be used --
+ * subject to CBS wakeup rules -- without having to wait for the next period.
+ *
+ * Additionally, because of the dl_defer behaviour the start/stop behaviour is
+ * naturally thottled to once per period, avoiding high context switch
+ * workloads from spamming the hrtimer program/cancel paths.
*/
extern void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec);
extern void dl_server_start(struct sched_dl_entity *dl_se);
--
2.54.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 6.12.y 0/3] backport missing dependencies of d66792919d4f
2026-05-22 21:31 [PATCH 6.12.y 0/3] backport missing dependencies of d66792919d4f Lukas Beckmann
` (2 preceding siblings ...)
2026-05-22 21:31 ` [PATCH 6.12.y 3/3] sched/deadline: Fix dl_server behaviour Lukas Beckmann
@ 2026-05-24 12:09 ` Sasha Levin
2026-05-25 21:09 ` Lukas Beckmann
3 siblings, 1 reply; 6+ messages in thread
From: Sasha Levin @ 2026-05-24 12:09 UTC (permalink / raw)
To: Lukas Beckmann
Cc: Sasha Levin, stable, regressions, Mike Galbraith, Peter Zijlstra,
Juri Lelli
> Commit d66792919d4f ("sched/deadline: Use revised wakeup rule for
> dl_server") in the 6.12.y stable tree (upstream commit 14a857056466)
> depends on three upstream commits that were not backported:
>
> commit cccb45d7c429 ("sched/deadline: Less agressive dl_server handling")
> commit 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
> commit a3a70caf7906 ("sched/deadline: Fix dl_server behaviour")
Thanks for tracking this down. Before I queue this, the series is
missing two more follow-up fixes that both carry "Fixes: cccb45d7c429"
and that are needed for the dl_server logic to behave correctly:
4717432dfd99 ("sched/deadline: Fix dl_server_stopped()")
bb4700adc3ab ("sched/deadline: Always stop dl-server before changing parameters")
Without 4717432dfd99 the dl_server_stopped() check is inverted (it
returns the wrong polarity after cccb45d7c429), and without
bb4700adc3ab the per-rq running_bw accounting can get out of sync when
dl-server parameters change while it is still active.
Could you send a v2 that includes both follow-ups on top of the
existing three? Then this should be safe to apply as a whole.
--
Thanks,
Sasha
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 6.12.y 0/3] backport missing dependencies of d66792919d4f
2026-05-24 12:09 ` [PATCH 6.12.y 0/3] backport missing dependencies of d66792919d4f Sasha Levin
@ 2026-05-25 21:09 ` Lukas Beckmann
0 siblings, 0 replies; 6+ messages in thread
From: Lukas Beckmann @ 2026-05-25 21:09 UTC (permalink / raw)
To: Sasha Levin
Cc: stable, regressions, Mike Galbraith, Peter Zijlstra, Juri Lelli
On Sun, May 24, 2026 at 08:09:19AM -0400, Sasha Levin wrote:
> > Commit d66792919d4f ("sched/deadline: Use revised wakeup rule for
> > dl_server") in the 6.12.y stable tree (upstream commit 14a857056466)
> > depends on three upstream commits that were not backported:
> >
> > commit cccb45d7c429 ("sched/deadline: Less agressive dl_server handling")
> > commit 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
> > commit a3a70caf7906 ("sched/deadline: Fix dl_server behaviour")
>
> Thanks for tracking this down. Before I queue this, the series is
> missing two more follow-up fixes that both carry "Fixes: cccb45d7c429"
> and that are needed for the dl_server logic to behave correctly:
>
> 4717432dfd99 ("sched/deadline: Fix dl_server_stopped()")
> bb4700adc3ab ("sched/deadline: Always stop dl-server before changing parameters")
>
> Without 4717432dfd99 the dl_server_stopped() check is inverted (it
> returns the wrong polarity after cccb45d7c429), and without
> bb4700adc3ab the per-rq running_bw accounting can get out of sync when
> dl-server parameters change while it is still active.
I did notice 4717432dfd99 while preparing v1, since it caused the
conflicts in a3a70caf7906. However, since 4ae8d9aa9f9d ("sched/deadline:
Fix dl_server getting stuck") removes dl_server_stopped() entirely, the
end result is the same whether 4717432dfd99 is included or not.
That said, including it is probably better :)
>
> Could you send a v2 that includes both follow-ups on top of the
> existing three? Then this should be safe to apply as a whole.
Yes, I will do that.
Thanks
Lukas
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2026-05-25 21:09 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-05-22 21:31 [PATCH 6.12.y 0/3] backport missing dependencies of d66792919d4f Lukas Beckmann
2026-05-22 21:31 ` [PATCH 6.12.y 1/3] sched/deadline: Less agressive dl_server handling Lukas Beckmann
2026-05-22 21:31 ` [PATCH 6.12.y 2/3] sched/deadline: Fix dl_server getting stuck Lukas Beckmann
2026-05-22 21:31 ` [PATCH 6.12.y 3/3] sched/deadline: Fix dl_server behaviour Lukas Beckmann
2026-05-24 12:09 ` [PATCH 6.12.y 0/3] backport missing dependencies of d66792919d4f Sasha Levin
2026-05-25 21:09 ` Lukas Beckmann
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox