Add a check for cpu unbound deferrable timer expiry and raise
softirq for handling the expired timers so that the CPU can
process the cpu unbound deferrable times as early as possible
when a cpu tries to enter/exit idle loop.
Signed-off-by: Prasad Sodagudi <[email protected]>
---
include/linux/timer.h | 3 +++
kernel/time/tick-sched.c | 8 +++++++-
kernel/time/timer.c | 29 ++++++++++++++++++++++++++++-
3 files changed, 38 insertions(+), 2 deletions(-)
diff --git a/include/linux/timer.h b/include/linux/timer.h
index 0dc19a8..e85dd2d 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -172,6 +172,9 @@ extern int del_timer(struct timer_list * timer);
extern int mod_timer(struct timer_list *timer, unsigned long expires);
extern int mod_timer_pending(struct timer_list *timer, unsigned long expires);
extern int timer_reduce(struct timer_list *timer, unsigned long expires);
+#ifdef CONFIG_SMP
+extern bool check_pending_deferrable_timers(int cpu);
+#endif
/*
* The jiffies value which is added to now, when there is no timer
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 3e2dc9b..16aec80 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -23,6 +23,7 @@
#include <linux/module.h>
#include <linux/irq_work.h>
#include <linux/posix-timers.h>
+#include <linux/timer.h>
#include <linux/context_tracking.h>
#include <linux/mm.h>
@@ -1274,8 +1275,13 @@ static inline void tick_nohz_irq_enter(void)
now = ktime_get();
if (ts->idle_active)
tick_nohz_stop_idle(ts, now);
- if (ts->tick_stopped)
+ if (ts->tick_stopped) {
tick_nohz_update_jiffies(now);
+#ifdef CONFIG_SMP
+ if (check_pending_deferrable_timers(smp_processor_id()))
+ raise_softirq_irqoff(TIMER_SOFTIRQ);
+#endif
+ }
}
#else
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 5ab8e33..c8327b4 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -221,6 +221,7 @@ static DECLARE_WORK(timer_update_work, timer_update_keys);
#ifdef CONFIG_SMP
struct timer_base timer_base_deferrable;
+static atomic_t deferrable_pending;
unsigned int sysctl_timer_migration = 1;
DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
@@ -1610,6 +1611,31 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
}
+
+#ifdef CONFIG_SMP
+/*
+ * check_pending_deferrable_timers - Check for unbound deferrable timer expiry
+ * @cpu - Current CPU
+ *
+ * The function checks whether any global deferrable pending timers
+ * are exipired or not. This function does not check cpu bounded
+ * diferrable pending timers expiry.
+ *
+ * The function returns true when a cpu unbounded deferrable timer is expired.
+ */
+bool check_pending_deferrable_timers(int cpu)
+{
+ if (cpu == tick_do_timer_cpu ||
+ tick_do_timer_cpu == TICK_DO_TIMER_NONE) {
+ if (time_after_eq(jiffies, timer_base_deferrable.clk)
+ && !atomic_cmpxchg(&deferrable_pending, 0, 1)) {
+ return true;
+ }
+ }
+ return false;
+}
+#endif
+
/**
* get_next_timer_interrupt - return the time (clock mono) of the next timer
* @basej: base time jiffies
@@ -1800,7 +1826,8 @@ static __latent_entropy void run_timer_softirq(struct softirq_action *h)
__run_timers(base);
if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) {
__run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
- if (tick_do_timer_cpu == TICK_DO_TIMER_NONE ||
+ if ((atomic_cmpxchg(&deferrable_pending, 1, 0) &&
+ tick_do_timer_cpu == TICK_DO_TIMER_NONE) ||
tick_do_timer_cpu == smp_processor_id())
__run_timers(&timer_base_deferrable);
}
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
Hi Prasad,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on tip/timers/core]
[also build test WARNING on tip/auto-latest tip/timers/nohz v5.7-rc3 next-20200428]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
url: https://github.com/0day-ci/linux/commits/Prasad-Sodagudi/timer-make-deferrable-cpu-unbound-timers-really-not-bound-to-a-cpu/20200429-060558
base: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 4479730e9263befbb9ce9563a09563db2acb8f7c
config: nds32-defconfig (attached as .config)
compiler: nds32le-linux-gcc (GCC) 9.3.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day GCC_VERSION=9.3.0 make.cross ARCH=nds32
If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <[email protected]>
All warnings (new ones prefixed by >>):
In file included from ./arch/nds32/include/generated/asm/cmpxchg.h:1,
from include/asm-generic/atomic.h:12,
from ./arch/nds32/include/generated/asm/atomic.h:1,
from include/linux/atomic.h:7,
from include/asm-generic/bitops/lock.h:5,
from include/asm-generic/bitops.h:31,
from ./arch/nds32/include/generated/asm/bitops.h:1,
from include/linux/bitops.h:29,
from include/linux/kernel.h:12,
from include/linux/list.h:9,
from include/linux/smp.h:12,
from include/linux/kernel_stat.h:5,
from kernel/time/timer.c:21:
kernel/time/timer.c: In function 'run_timer_softirq':
kernel/time/timer.c:1828:24: error: 'deferrable_pending' undeclared (first use in this function)
1828 | if ((atomic_cmpxchg(&deferrable_pending, 1, 0) &&
| ^~~~~~~~~~~~~~~~~~
include/asm-generic/cmpxchg.h:97:17: note: in definition of macro 'cmpxchg_local'
97 | ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
| ^~~
>> include/asm-generic/atomic.h:196:38: note: in expansion of macro 'cmpxchg'
196 | #define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))
| ^~~~~~~
>> kernel/time/timer.c:1828:8: note: in expansion of macro 'atomic_cmpxchg'
1828 | if ((atomic_cmpxchg(&deferrable_pending, 1, 0) &&
| ^~~~~~~~~~~~~~
kernel/time/timer.c:1828:24: note: each undeclared identifier is reported only once for each function it appears in
1828 | if ((atomic_cmpxchg(&deferrable_pending, 1, 0) &&
| ^~~~~~~~~~~~~~~~~~
include/asm-generic/cmpxchg.h:97:17: note: in definition of macro 'cmpxchg_local'
97 | ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
| ^~~
>> include/asm-generic/atomic.h:196:38: note: in expansion of macro 'cmpxchg'
196 | #define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))
| ^~~~~~~
>> kernel/time/timer.c:1828:8: note: in expansion of macro 'atomic_cmpxchg'
1828 | if ((atomic_cmpxchg(&deferrable_pending, 1, 0) &&
| ^~~~~~~~~~~~~~
kernel/time/timer.c:1831:18: error: 'timer_base_deferrable' undeclared (first use in this function)
1831 | __run_timers(&timer_base_deferrable);
| ^~~~~~~~~~~~~~~~~~~~~
kernel/time/timer.c: In function 'init_timer_deferrable_global':
kernel/time/timer.c:2073:2: error: 'timer_base_deferrable' undeclared (first use in this function)
2073 | timer_base_deferrable.cpu = nr_cpu_ids;
| ^~~~~~~~~~~~~~~~~~~~~
vim +/atomic_cmpxchg +1828 kernel/time/timer.c
1817
1818 /*
1819 * This function runs timers and the timer-tq in bottom half context.
1820 */
1821 static __latent_entropy void run_timer_softirq(struct softirq_action *h)
1822 {
1823 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1824
1825 __run_timers(base);
1826 if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) {
1827 __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
> 1828 if ((atomic_cmpxchg(&deferrable_pending, 1, 0) &&
1829 tick_do_timer_cpu == TICK_DO_TIMER_NONE) ||
1830 tick_do_timer_cpu == smp_processor_id())
1831 __run_timers(&timer_base_deferrable);
1832 }
1833 }
1834
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/[email protected]
Hi Prasad,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on tip/timers/core]
[also build test ERROR on tip/auto-latest tip/timers/nohz v5.7-rc3 next-20200428]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
url: https://github.com/0day-ci/linux/commits/Prasad-Sodagudi/timer-make-deferrable-cpu-unbound-timers-really-not-bound-to-a-cpu/20200429-060558
base: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 4479730e9263befbb9ce9563a09563db2acb8f7c
config: i386-tinyconfig (attached as .config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce:
# save the attached .config to linux build tree
make ARCH=i386
If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <[email protected]>
All errors (new ones prefixed by >>):
kernel/time/timer.c: In function 'run_timer_softirq':
>> kernel/time/timer.c:1828:24: error: 'deferrable_pending' undeclared (first use in this function); did you mean 'detach_if_pending'?
if ((atomic_cmpxchg(&deferrable_pending, 1, 0) &&
^~~~~~~~~~~~~~~~~~
detach_if_pending
kernel/time/timer.c:1828:24: note: each undeclared identifier is reported only once for each function it appears in
kernel/time/timer.c:1831:18: error: 'timer_base_deferrable' undeclared (first use in this function); did you mean 'timer_base_lock_expiry'?
__run_timers(&timer_base_deferrable);
^~~~~~~~~~~~~~~~~~~~~
timer_base_lock_expiry
kernel/time/timer.c: In function 'init_timer_deferrable_global':
kernel/time/timer.c:2073:2: error: 'timer_base_deferrable' undeclared (first use in this function); did you mean 'timer_base_lock_expiry'?
timer_base_deferrable.cpu = nr_cpu_ids;
^~~~~~~~~~~~~~~~~~~~~
timer_base_lock_expiry
vim +1828 kernel/time/timer.c
1817
1818 /*
1819 * This function runs timers and the timer-tq in bottom half context.
1820 */
1821 static __latent_entropy void run_timer_softirq(struct softirq_action *h)
1822 {
1823 struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1824
1825 __run_timers(base);
1826 if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) {
1827 __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
> 1828 if ((atomic_cmpxchg(&deferrable_pending, 1, 0) &&
1829 tick_do_timer_cpu == TICK_DO_TIMER_NONE) ||
1830 tick_do_timer_cpu == smp_processor_id())
1831 __run_timers(&timer_base_deferrable);
1832 }
1833 }
1834
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/[email protected]