Bug 1745646
| Summary: | [RT] sched/fair: Robustify CFS-bandwidth timer locking | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 8 | Reporter: | Clark Williams <williams> |
| Component: | kernel-rt | Assignee: | Clark Williams <williams> |
| kernel-rt sub component: | Scheduler | QA Contact: | Qiao Zhao <qzhao> |
| Status: | CLOSED ERRATA | Docs Contact: | |
| Severity: | high | ||
| Priority: | unspecified | CC: | bhu, jlelli, lgoncalv, mstowell, qzhao, tieli |
| Version: | 8.1 | ||
| Target Milestone: | rc | ||
| Target Release: | 8.0 | ||
| Hardware: | x86_64 | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | kernel-rt-4.18.0-80.5.rt16.1.el8 | Doc Type: | No Doc Update |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2019-11-05 20:38:26 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | |||
| Bug Blocks: | 1696402 | ||
Upstream commit from PREEMPT_RT tree: c0ad4aa4d8 The code from commit c0ad4aa4d8 got pulled in with other 5.2-rt backports, so this is mainly relevant for pulling back to zstreams (In reply to Clark Williams from comment #2) > The code from commit c0ad4aa4d8 got pulled in with other 5.2-rt backports, > so this is mainly relevant for pulling back to zstreams kernel-rt-4.18.0-80.5.rt16.1.el8 (2019-03-27) and newer contains this commit Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHSA-2019:3309 |
This commit fixes a system lockup that happens with no system log reporting and affects all Red Hat RT kernels. From the commit log: Traditionally hrtimer callbacks were run with IRQs disabled, but with the introduction of HRTIMER_MODE_SOFT it is possible they run from SoftIRQ context, which does _NOT_ have IRQs disabled. Allow for the CFS bandwidth timers (period_timer and slack_timer) to be ran from SoftIRQ context; this entails removing the assumption that IRQs are already disabled from the locking. While mainline doesn't strictly need this, -RT forces all timers not explicitly marked with MODE_HARD into MODE_SOFT and trips over this. And marking these timers as MODE_HARD doesn't make sense as they're not required for RT operation and can potentially be quite expensive. Reported-by: Tom Putzeys <tom.putzeys.com> Tested-by: Mike Galbraith <efault> Signed-off-by: Peter Zijlstra (Intel) <peterz> Cc: Linus Torvalds <torvalds> Cc: Peter Zijlstra <peterz> Cc: Sebastian Andrzej Siewior <bigeasy> Cc: Thomas Gleixner <tglx> Link: https://lkml.kernel.org/r/20190107125231.GE14122@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo>