redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

A single fix in for hrtimers to prevent an interrupt storm caused by the 

lack of reevaluation of the timers which expire in softirq context under
 certain circumstances, e.g. when the clock was set.
 -----BEGIN PGP SIGNATURE-----
 
 iQJHBAABCgAxFiEEQp8+kY+LLUocC4bMphj1TA10mKEFAmBOLKkTHHRnbHhAbGlu
 dXRyb25peC5kZQAKCRCmGPVMDXSYoeypD/wL+NjxFXzmAaSsy/sehpEmkavixQlE
 BCfW+pVIvj4Hs4OQyzhJVdRIos/hzU+P/xmZ8Mk+yBU6+SY6n8N/CODzhV2IbaXT
 V90MFqyB4U0/eWlILpAoVNxl+3SHvX1HxkrQn1uEz5+643tS9gnatlCAUGwHDzLD
 i0Jykvpd9ytHi7VRPconzIA0wsG/DGkgQ7yzX+lLrhg6J/D04uTwT3j4nw9pgCH4
 lsc3Snv+RoGwrcgNbgueRXxdIExPw0NfDOC2dM7SWWcgHXGK7MOt/WkrvD8xHF6c
 CaF1Q2MXgZDjBynYzjFgSsHwk6iUc6X4EdxgA2fskQnSD8GhI88H875hIQJ2bF1r
 jZS2UyDXKnaddOjKhigx3tQs3F2TjArKBxreP3oIzfTGCDE7t5tAo8siPvsHSB0E
 FvuhSf3wojVCoLbsd+ByGH/Deh2Qe13eG8arG2pell7OBzCj/wU5Luw6K4uHAmFh
 1cMnmOt8zeUkm7HPZX8fiZZlRDKqldBOZ5Mc7kEJ1sOzxtmxMYHRqGlFKhvByDrH
 x/41WiJMskK+L/aqBOQZz5Yqn1PRGWDvLUpgFXFGeQeJaDDNB6dFvlXTfR6hUbdd
 LKdrNMQk+E/o5+tZwhymz6+OXYlzoUZTU2FljwL8dLog7wRNhtFbsESFuI5nkJuN
 MIZm1+5Lr4TNVg==
 =GZmg
 -----END PGP SIGNATURE-----

Merge tag 'timers-urgent-2021-03-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer fix from Thomas Gleixner:
 "A single fix in for hrtimers to prevent an interrupt storm caused by
  the lack of reevaluation of the timers which expire in softirq context
  under certain circumstances, e.g. when the clock was set"

* tag 'timers-urgent-2021-03-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  hrtimer: Update softirq_expires_next correctly after __hrtimer_get_next_event()
rM2-mainline
Linus Torvalds 2021-03-14 13:29:38 -07:00
parent c72cbc9361 46eb1701c0
commit 802b31c0dd
1 changed files with 39 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
kernel/time/hrtimer.c
View File

@ -546,8 +546,11 @@ static ktime_t __hrtimer_next_event_base(struct hrtimer_cpu_base *cpu_base,
}
/*
* Recomputes cpu_base::*next_timer and returns the earliest expires_next but
* does not set cpu_base::*expires_next, that is done by hrtimer_reprogram.
* Recomputes cpu_base::*next_timer and returns the earliest expires_next
* but does not set cpu_base::*expires_next, that is done by
* hrtimer[_force]_reprogram and hrtimer_interrupt only. When updating
* cpu_base::*expires_next right away, reprogramming logic would no longer
* work.
*
* When a softirq is pending, we can ignore the HRTIMER_ACTIVE_SOFT bases,
* those timers will get run whenever the softirq gets handled, at the end of
@ -588,6 +591,37 @@ __hrtimer_get_next_event(struct hrtimer_cpu_base *cpu_base, unsigned int active_
return expires_next;
}
static ktime_t hrtimer_update_next_event(struct hrtimer_cpu_base *cpu_base)
{
ktime_t expires_next, soft = KTIME_MAX;
/*
* If the soft interrupt has already been activated, ignore the
* soft bases. They will be handled in the already raised soft
* interrupt.
*/
if (!cpu_base->softirq_activated) {
soft = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_SOFT);
/*
* Update the soft expiry time. clock_settime() might have
* affected it.
*/
cpu_base->softirq_expires_next = soft;
}
expires_next = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_HARD);
/*
* If a softirq timer is expiring first, update cpu_base->next_timer
* and program the hardware with the soft expiry time.
*/
if (expires_next > soft) {
cpu_base->next_timer = cpu_base->softirq_next_timer;
expires_next = soft;
}
return expires_next;
}
static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
{
ktime_t *offs_real = &base->clock_base[HRTIMER_BASE_REALTIME].offset;
@ -628,23 +662,7 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
{
ktime_t expires_next;
/*
* Find the current next expiration time.
*/
expires_next = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_ALL);
if (cpu_base->next_timer && cpu_base->next_timer->is_soft) {
/*
* When the softirq is activated, hrtimer has to be
* programmed with the first hard hrtimer because soft
* timer interrupt could occur too late.
*/
if (cpu_base->softirq_activated)
expires_next = __hrtimer_get_next_event(cpu_base,
HRTIMER_ACTIVE_HARD);
else
cpu_base->softirq_expires_next = expires_next;
}
expires_next = hrtimer_update_next_event(cpu_base);
if (skip_equal && expires_next == cpu_base->expires_next)
return;
@ -1644,8 +1662,8 @@ retry:
__hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD);
/* Reevaluate the clock bases for the next expiry */
expires_next = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_ALL);
/* Reevaluate the clock bases for the [soft] next expiry */
expires_next = hrtimer_update_next_event(cpu_base);
/*
* Store the new expiry value so the migration code can verify
* against it.