From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Fri, 14 Aug 2020 21:17:51 +0000 (-0700)
Subject: Merge tag 'timers-core-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git... 
X-Git-Tag: v5.15~3090
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=b6b178e38f40f34842b719a8786d346d4cfec5dc;hp=-c;p=platform%2Fkernel%2Flinux-starfive.git

Merge tag 'timers-core-2020-08-14' of git://git./linux/kernel/git/tip/tip

Pull more timer updates from Thomas Gleixner:
 "A set of posix CPU timer changes which allows to defer the heavy work
  of posix CPU timers into task work context. The tick interrupt is
  reduced to a quick check which queues the work which is doing the
  heavy lifting before returning to user space or going back to guest
  mode. Moving this out is deferring the signal delivery slightly but
  posix CPU timers are inaccurate by nature as they depend on the tick
  so there is no real damage. The relevant test cases all passed.

  This lifts the last offender for RT out of the hard interrupt context
  tick handler, but it also has the general benefit that the actual
  heavy work is accounted to the task/process and not to the tick
  interrupt itself.

  Further optimizations are possible to break long sighand lock hold and
  interrupt disabled (on !RT kernels) times when a massive amount of
  posix CPU timers (which are unpriviledged) is armed for a
  task/process.

  This is currently only enabled for x86 because the architecture has to
  ensure that task work is handled in KVM before entering a guest, which
  was just established for x86 with the new common entry/exit code which
  got merged post 5.8 and is not the case for other KVM architectures"

* tag 'timers-core-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86: Select POSIX_CPU_TIMERS_TASK_WORK
  posix-cpu-timers: Provide mechanisms to defer timer handling to task_work
  posix-cpu-timers: Split run_posix_cpu_timers()
---

b6b178e38f40f34842b719a8786d346d4cfec5dc
diff --combined arch/x86/Kconfig
index 9a28495,a82e715..7101ac6
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@@ -209,6 -209,7 +209,7 @@@ config X8
  	select HAVE_PERF_REGS
  	select HAVE_PERF_USER_STACK_DUMP
  	select MMU_GATHER_RCU_TABLE_FREE		if PARAVIRT
+ 	select HAVE_POSIX_CPU_TIMERS_TASK_WORK
  	select HAVE_REGS_AND_STACK_ACCESS_API
  	select HAVE_RELIABLE_STACKTRACE		if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION
  	select HAVE_FUNCTION_ARG_ACCESS_API
@@@ -803,7 -804,6 +804,7 @@@ config KVM_GUES
  	depends on PARAVIRT
  	select PARAVIRT_CLOCK
  	select ARCH_CPUIDLE_HALTPOLL
 +	select X86_HV_CALLBACK_VECTOR
  	default y
  	help
  	  This option enables various optimizations for running under the KVM
diff --combined include/linux/sched.h
index 53ddc02,e9942ce..93ecd930
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@@ -32,7 -32,6 +32,7 @@@
  #include <linux/task_io_accounting.h>
  #include <linux/posix-timers.h>
  #include <linux/rseq.h>
 +#include <linux/seqlock.h>
  #include <linux/kcsan.h>
  
  /* task_struct member predeclarations (sorted alphabetically): */
@@@ -890,6 -889,10 +890,10 @@@ struct task_struct 
  	/* Empty if CONFIG_POSIX_CPUTIMERS=n */
  	struct posix_cputimers		posix_cputimers;
  
+ #ifdef CONFIG_POSIX_CPU_TIMERS_TASK_WORK
+ 	struct posix_cputimers_work	posix_cputimers_work;
+ #endif
+ 
  	/* Process credentials: */
  
  	/* Tracer's credentials at attach: */
@@@ -1050,7 -1053,7 +1054,7 @@@
  	/* Protected by ->alloc_lock: */
  	nodemask_t			mems_allowed;
  	/* Seqence number to catch updates: */
 -	seqcount_t			mems_allowed_seq;
 +	seqcount_spinlock_t		mems_allowed_seq;
  	int				cpuset_mem_spread_rotor;
  	int				cpuset_slab_spread_rotor;
  #endif
@@@ -1649,9 -1652,6 +1653,9 @@@ extern int idle_cpu(int cpu)
  extern int available_idle_cpu(int cpu);
  extern int sched_setscheduler(struct task_struct *, int, const struct sched_param *);
  extern int sched_setscheduler_nocheck(struct task_struct *, int, const struct sched_param *);
 +extern void sched_set_fifo(struct task_struct *p);
 +extern void sched_set_fifo_low(struct task_struct *p);
 +extern void sched_set_normal(struct task_struct *p, int nice);
  extern int sched_setattr(struct task_struct *, const struct sched_attr *);
  extern int sched_setattr_nocheck(struct task_struct *, const struct sched_attr *);
  extern struct task_struct *idle_task(int cpu);