[GIT PULL] scheduler fixes

Ingo Molnar
2018-02-15T01:01:05Z

Linus,

Please pull the latest sched-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-for-linus

# HEAD: 43d1b29b27c76e7454cd6c85bec4d0e9cbb039f3 sched/cpufreq: Remove unused SUGOV_KTHREAD_PRIORITY macro

Misc fixes:

- fix rq->lock lockdep annotation bug
- fix/improve update_curr_rt() and update_curr_dl() accounting
- update documentation
- remove unused macro

Thanks,

Ingo

------------------>
Leo Yan (1):
sched/cpufreq: Remove unused SUGOV_KTHREAD_PRIORITY macro

Mathieu Desnoyers (1):
membarrier-sync-core: Document architecture support

Peter Zijlstra (1):
sched/core: Fix DEBUG_SPINLOCK annotation for rq->lock

Wen Yang (2):
sched/deadline: Make update_curr_dl() more accurate
sched/rt: Make update_curr_rt() more accurate

.../sched/membarrier-sync-core/arch-support.txt | 62 ++++++++++++++++++++++
kernel/sched/core.c | 27 ++++++----
kernel/sched/cpufreq_schedutil.c | 2 -
kernel/sched/deadline.c | 6 ++-
kernel/sched/rt.c | 3 +-
5 files changed, 84 insertions(+), 16 deletions(-)
create mode 100644 Documentation/features/sched/membarrier-sync-core/arch-support.txt

diff --git a/Documentation/features/sched/membarrier-sync-core/arch-support.txt b/Documentation/features/sched/membarrier-sync-core/arch-support.txt
new file mode 100644
index 000000000000..2c815a7f1ba7
--- /dev/null
+++ b/Documentation/features/sched/membarrier-sync-core/arch-support.txt
@@ -0,0 +1,62 @@
+#
+# Feature name: membarrier-sync-core
+# Kconfig: ARCH_HAS_MEMBARRIER_SYNC_CORE
+# description: arch supports core serializing membarrier
+#
+# Architecture requirements
+#
+# * arm64
+#
+# Rely on eret context synchronization when returning from IPI handler, and
+# when returning to user-space.
+#
+# * x86
+#
+# x86-32 uses IRET as return from interrupt, which takes care of the IPI.
+# However, it uses both IRET and SYSEXIT to go back to user-space. The IRET
+# instruction is core serializing, but not SYSEXIT.
+#
+# x86-64 uses IRET as return from interrupt, which takes care of the IPI.
+# However, it can return to user-space through either SYSRETL (compat code),
+# SYSRETQ, or IRET.
+#
+# Given that neither SYSRET{L,Q}, nor SYSEXIT, are core serializing, we rely
+# instead on write_cr3() performed by switch_mm() to provide core serialization
+# after changing the current mm, and deal with the special case of kthread ->
+# uthread (temporarily keeping current mm into active_mm) by issuing a
+# sync_core_before_usermode() in that specific case.
+#
+ -----------------------
+ | arch |status|
+ -----------------------
+ | alpha: | TODO |
+ | arc: | TODO |
+ | arm: | TODO |
+ | arm64: | ok |
+ | blackfin: | TODO |
+ | c6x: | TODO |
+ | cris: | TODO |
+ | frv: | TODO |
+ | h8300: | TODO |
+ | hexagon: | TODO |
+ | ia64: | TODO |
+ | m32r: | TODO |
+ | m68k: | TODO |
+ | metag: | TODO |
+ | microblaze: | TODO |
+ | mips: | TODO |
+ | mn10300: | TODO |
+ | nios2: | TODO |
+ | openrisc: | TODO |
+ | parisc: | TODO |
+ | powerpc: | TODO |
+ | s390: | TODO |
+ | score: | TODO |
+ | sh: | TODO |
+ | sparc: | TODO |
+ | tile: | TODO |
+ | um: | TODO |
+ | unicore32: | TODO |
+ | x86: | ok |
+ | xtensa: | TODO |
+ -----------------------
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index bf724c1952ea..e7c535eee0a6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2601,19 +2601,31 @@ static inline void finish_task(struct task_struct *prev)
#endif
}

-static inline void finish_lock_switch(struct rq *rq)
+static inline void
+prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
{
+ /*
+ * Since the runqueue lock will be released by the next
+ * task (which is an invalid locking op but in the case
+ * of the scheduler it's an obvious special-case), so we
+ * do an early lockdep release here:
+ */
+ rq_unpin_lock(rq, rf);
+ spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
#ifdef CONFIG_DEBUG_SPINLOCK
/* this is a valid case when another task releases the spinlock */
- rq->lock.owner = current;
+ rq->lock.owner = next;
#endif
+}
+
+static inline void finish_lock_switch(struct rq *rq)
+{
/*
* If we are tracking spinlock dependencies then we have to
* fix up the runqueue lock - which gets 'carried over' from
* prev into current:
*/
spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);
-
raw_spin_unlock_irq(&rq->lock);
}

@@ -2844,14 +2856,7 @@ context_switch(struct rq *rq, struct task_struct *prev,

rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);

- /*
- * Since the runqueue lock will be released by the next
- * task (which is an invalid locking op but in the case
- * of the scheduler it's an obvious special-case), so we
- * do an early lockdep release here:
- */
- rq_unpin_lock(rq, rf);
- spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
+ prepare_lock_switch(rq, next, rf);

/* Here we just switch the register state and the stack. */
switch_to(prev, next, prev);
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index dd062a1c8cf0..7936f548e071 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -19,8 +19,6 @@

#include "sched.h"

-#define SUGOV_KTHREAD_PRIORITY 50
-
struct sugov_tunables {
struct gov_attr_set attr_set;
unsigned int rate_limit_us;
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 9bb0e0c412ec..9df09782025c 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1153,6 +1153,7 @@ static void update_curr_dl(struct rq *rq)
struct sched_dl_entity *dl_se = &curr->dl;
u64 delta_exec, scaled_delta_exec;
int cpu = cpu_of(rq);
+ u64 now;

if (!dl_task(curr) || !on_dl_rq(dl_se))
return;
@@ -1165,7 +1166,8 @@ static void update_curr_dl(struct rq *rq)
* natural solution, but the full ramifications of this
* approach need further study.
*/
- delta_exec = rq_clock_task(rq) - curr->se.exec_start;
+ now = rq_clock_task(rq);
+ delta_exec = now - curr->se.exec_start;
if (unlikely((s64)delta_exec <= 0)) {
if (unlikely(dl_se->dl_yielded))
goto throttle;
@@ -1178,7 +1180,7 @@ static void update_curr_dl(struct rq *rq)
curr->se.sum_exec_runtime += delta_exec;
account_group_exec_runtime(curr, delta_exec);

- curr->se.exec_start = rq_clock_task(rq);
+ curr->se.exec_start = now;
cgroup_account_cputime(curr, delta_exec);

sched_rt_avg_update(rq, delta_exec);
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 663b2355a3aa..aad49451584e 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -950,12 +950,13 @@ static void update_curr_rt(struct rq *rq)
{
struct task_struct *curr = rq->curr;
struct sched_rt_entity *rt_se = &curr->rt;
- u64 now = rq_clock_task(rq);
u64 delta_exec;
+ u64 now;

if (curr->sched_class != &rt_sched_class)
return;

+ now = rq_clock_task(rq);
delta_exec = now - curr->se.exec_start;
if (unlikely((s64)delta_exec <= 0))
return;