[Bug 754186] New: rcu stalls (?) cause hung tasks
https://bugzilla.novell.com/show_bug.cgi?id=754186 https://bugzilla.novell.com/show_bug.cgi?id=754186#c0 Summary: rcu stalls (?) cause hung tasks Classification: openSUSE Product: openSUSE 12.2 Version: Milestone 2 Platform: x86-64 OS/Version: Other Status: NEW Severity: Major Priority: P5 - None Component: Kernel AssignedTo: mgalbraith@suse.com ReportedBy: jeffm@suse.com QAContact: qa-bugs@suse.de Found By: Development Blocker: --- Created an attachment (id=483348) --> (http://bugzilla.novell.com/attachment.cgi?id=483348) Log Using kernel 3.3.0-3-desktop, rcu stalls are causing hung tasks. -- Configure bugmail: https://bugzilla.novell.com/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.
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--- Comment #2 from Mike Galbraith
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--- Comment #3 from Mike Galbraith
Hm, wlan0 starts coming up, RT throttle kicks in and the fun begins.
patches.fixes/sched-rtsched_debug-boot-option.patch may help. Would also be interesting to turn off RCU_BOOST. If the throttle is kicking in, trying to boost via an RT thread isn't going to work well.
Seeing systemd... If systemd were to move a task into a cgroup with no rt_runtime, and then RCU boost kicks in, the boosted task will never be able to run. See mainline 7abc63b1 sched/rt: Do not throttle when PI boosting -- Configure bugmail: https://bugzilla.novell.com/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.
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Jeff Mahoney
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Jeff Mahoney
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--- Comment #6 from Mike Galbraith
Created an attachment (id=483549) --> (http://bugzilla.novell.com/attachment.cgi?id=483549) [details] Updated log
This log doesn't have any traces in it, but the "RT: throttling CPU1" messages started nearly immediately after boot. When I rebooted it, it was responding to pings but wouldn't allow logins or su. Switching to VT1 hung the console.
Ok, RT utilization isn't reaching the threshold to start issuing danger warnings. I'll build this kernel on my laptop, see if I can reproduce too, and bend the throttle warning patchlet up to give more info. There's also another rt throttle patch I have tagged for audit time.. let me hunt that down.. ah, here it is, duh, right next to the previous one, another that is not stable tagged, but imho should have been. 42c62a58 sched/rt: Keep period timer ticking when rt throttling is active -- Configure bugmail: https://bugzilla.novell.com/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.
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--- Comment #7 from Mike Galbraith
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Jeff Mahoney
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Jeff Mahoney
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--- Comment #10 from Mike Galbraith
This one seems to have had an impact. Thanks!
Goodie, so it was a dead bug. Those are the easiest kind to kill ;-) -- Configure bugmail: https://bugzilla.novell.com/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.
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--- Comment #11 from Mike Galbraith
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--- Comment #12 from Swamp Workflow Management
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--- Comment #13 from Swamp Workflow Management
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