For multiple continuous RCU stalls, all sampling > + periods begin at half of the first RCU stall timeout. 0: (1 GPs behind) idle=bf2/140000000000000/0 softirq=554/555 fqs=6754 (detected by 1, t=21003 jiffies, g=-154, c=-155, q=120339) Sending NMI from CPU 1 to CPUs 0:. Uplock Roller (RG) Warning cam. Aligns the output of the last line of RCU stall. 3. 22 ມິ. This document first discusses what sorts of issues RCU’s CPU stall detector can locate, and then discusses kernel parameters and Kconfig options that can be used to fine-tune the detector’s operation. 12 with some local. A small debug dump excerpt from the console characterising every stall, copied by hand (in case of any errors and for a detailed trace please consult this image): INFO: rcu_preempt detected stalls on CPUs/tasks: { 0} (detected by 1, t=2102 jiffies, g=50012, c=50011, q=6543) [<8077bd70>] (__schedule) from [<80a7ffa0>] (init_thread_union+0x1fa0. org> Date: Mon, 9 Oct 2017 20:39:57 -0400: List-archive:. Web. Update comments and document. kernel running on these machines is based on 3. detector, which detects conditions that unduly delay RCU grace periods. The next question is “What caused it?” The following problems can result in RCU CPU stall warnings: A CPU looping in an RCU read-side critical section. The issue occurrence is random but exists. When Block Design added a AXI-DMA/AXI-VDMA IP core cause kernel startup reports “RCU: INFO: rcu_sched detected stalls on CPUs/tasks: ”. No code change. In the vast majority of cases, real-time users face RCU stalls due to the delay of RCU callbacks execution. Resolve a git am conflict. the in-band kernel may eventually complain about a RCU stall. Aligns the output of the last line of RCU stall. Resolve a git am conflict. 14 ++- kernel/rcu/Kconfig. net, tim. INFO: rcu_preempt detected stalls on CPUs/tasks: 2021-11-15T09:47:25Z xi-1B-D8-3E user. Aligns the output of the last line of RCU stall. Feb 10, 2020 · The issue occurrence is random but exists. The stall detector's idea of what constitutes "unduly delayed" is. > > > > Fair enough, will take that approach! > > > > I am thinking in terms of something like the following: > > > > RCU_FLAVOR > > RCU_BH_FLAVOR > > RCU_SCHED. 5-linode48 #1 Call Trace: 0 forum:zunzun 9 years, 11 months ago After a recent reboot, I see high CPU for a process named rcu_sched. v3 --> v4: 1. panic_on_rcu_stall = 1" >> /etc/sysctl. Web. McKenney wrote: > > > And here is a patch. 62 Beta BSP. v3 --> v4: 1. An example is the SyndicationClient sample. This example of stall. First Seen. soft lockups:. v3 --> v4: 1. Soft lockups and RCU sched CPU stalls are detected where many CPUs are looping in a spinlock. Please note that PREEMPT_RCU builds can be stalled by tasks as well as by CPUs, and that the tasks will be indicated by PID, for example, “P3421”. Web. 462843] 13-. v5 --> v6: 1. conf # sysctl -p When the kernel. The impact on system performance is negligible because snapshot is recorded only once for all continuous RCU stalls. If the rcu stall is detected by another CPU, > kcpustat_this_cpu cannot be used. Finally, this document explains the stall detector's "splat" format. panic_on_rcu_stall parameter added to sysctl to debug RCU stalls on a vmcore. Description of problem: Kernel emits RCU stall messages if a RT task with priority higher than or equals to FIFO:2 runs for more than 60 seconds. > > 3. Just for debugging purpose, can you try disabling CPU IDLE from kernel config and see if stall issue goes away?. Thanks!-- Florian #include <stdlib. Add comments and normalize local variable name v1 --> v2: 1. Thanks!-- Florian #include <stdlib. 123 with Imx6Q processor, we are getting rcu_preempt error and cpu hangs, The HW doesnt have HDMI or any on screen dispay, however the device had configurations and device tree for, GPU and HDMI enabled. Resolve a git am conflict. Check our new training course. v4 --> v5: 1. Update comments and document. v5 --> v6: 1. 457729] 3-. tj; pd. Move the start point of statistics from rcu_stall_kick_kthreads() to rcu_implicit_dynticks_qs(), removing the dependency on irq_work. The rcu_cpu_stall_suppress module parameter enables RCU's CPU stall. Booting with 38400bps, plus enabling CONFIG_RCU_FAST_NO_HZ and CONFIG_RCU_NOCB_CPU. v1: In some extreme cases, such as the I/O pressure test, the CPU usage may be 100%, causing RCU stall. h> #include <stdio. This capability is enabled by a new config variable CONFIG_RCU_CPU_STALL_DETECTOR, which defaults disabled. Aligns the output of the last line of RCU stall. v5 --> v6: 1. Using RCU’s CPU Stall Detector. [ 3. + bool "Provide additional rcu stall debug information" + depends on RCU_STALL_COMMON + default n + help + Statistics during the period from RCU_CPU_STALL_TIMEOUT/2 to + RCU_CPU_STALL_TIMEOUT, such as the number of (hard interrupts, soft + interrupts, task switches) and the cputime of (hard interrupts, soft. The RCU callbacks are responsible for performing the necessary RCU work to achieve the end of a grace period. A small debug dump excerpt from the console characterising every stall, copied by hand (in case of any errors and for a detailed trace please consult this image): INFO: rcu_preempt detected stalls on CPUs/tasks: { 0} (detected by 1, t=2102 jiffies, g=50012, c=50011, q=6543) [<8077bd70>] (__schedule) from [<80a7ffa0>] (init_thread_union+0x1fa0. org help / color / mirror / Atom feed * [PATCH] rcu: Add cpu-exp indicator to expedited RCU CPU stall warnings @ 2022-05-18 11:43 Zqiang 2022-05-18 18:14 ` Paul E. Thanks to Elliott, Robert for the test. 320064] rcu: blocking rcu_node structures (internal RCU debug):. is running at a higher priority than the RCU softirq threads. 23 ມ. Web. com> To:: herbert-AT-gondor. v2 --> v3: 1. Thanks to Elliott, Robert for the test. In this case, the printed information about current is not useful. This feature can detect looping CPUs in !PREEMPT builds and looping CPUs with preemption disabled in PREEMPT builds. v5 --> v6: 1. Although a RCU Stall can be a side effect of a kernel BUG, this is not the typical case for the real-time kernel users. When there are more than two continuous RCU stallings, correctly handle the value of the second and subsequent sampling periods. Anyway, your thread seems to have been held up for 59 seconds (assuming a 250 hertz kernel). [ 95. This message will normally be followed by stack dumps for each CPU. Sometimes we observe RCU stall warnings immediately after device boots up and sometimes we observe after running the device for longs hours (> 12 hours). arrays, and even to get offlined altogether by the SCSI layer. When there are more than two continuous RCU stallings, correctly handle the value of the second and subsequent sampling periods. h> #include <string. Nov 04, 2022 · Rename rcu_cpu_stall_deep_debug to rcu_cpu_stall_cputime. v5 --> v6: 1. v5 --> v6: 1. org help / color / mirror / Atom feed * [PATCH] rcu: Add cpu-exp indicator to expedited RCU CPU stall warnings @ 2022-05-18 11:43 Zqiang 2022-05-18 18:14 ` Paul E. Add Kconfig option CONFIG_RCU_CPU_STALL_DEEP_DEBUG and boot parameter rcupdate. : (52300 ticks this GP) idle=439/140000000000001/ softirq=806264/806264 fqs=52291 INFO:. Web. Soft lockups and RCU sched CPU stalls are detected where many CPUs are looping in a spinlock. Unfortunately there is no debug utility present in the controller . We have seen a recent uptick in reports of rcu_sched stalls with kernel panics Maybe we are running into this issue more often as the core counts go up on these processors. rcu_sched stall OR kernel panic on PowerEdge R640. h > index 96122f203187f39. Finally, this document explains the stall detector’s “splat” format. The command "dmesg | grep torture:" will extract this information on most systems. In the vast majority of cases, real-time users face RCU stalls due to the delay of RCU callbacks execution. The kernel includes an RCU stall detection. 62 Beta BSP. It takes about 4 hours and cost of 13,000 KRW. is running at a higher priority than the RCU softirq threads. [Bug 1796217] Re: Qunata server memory stress cause "rcu_sched detected stalls on cpus/tasks" Joseph Salisbury Tue, 09 Oct 2018 09:27:36 -0700. Add Kconfig option CONFIG_RCU_CPU_STALL_DEEP_DEBUG and boot parameter > rcupdate. This is quite unlikely, but has occurred at least once in real life. Resolve a git am conflict. In this case, the printed information about current is not useful. Add Kconfig option CONFIG_RCU_CPU_STALL_DEEP_DEBUG and boot parameter rcupdate. Web. A "grace period" must elapse between the two parts, and this grace period must be long enough that any readers. from [Joshua Kinard] [Permanent Link] To: Linux/MIPS <linux-mips@linux-mips. v4 --> v5: 1. v5 --> v6: 1. v5 --> v6: 1. Change "rcu stall" to "RCU stall". OK, let's take a look at the stall warning. Sep 12, 2017 · Decoding Those Inscrutable RCU CPU Stall Warnings, September 12, 2017 Example RCU CPU Stall Warning Splat (First Format) INFO: rcu_sched detected stalls on CPUs/tasks: 0-. 739296] Task dump for CPU 0: [ . This document. 19 ພ. Thanks!-- Florian #include <stdlib. Web. Fix the return type of kstat_cpu_irqs_sum () 2. : (20999 ticks this GP) idle=042/1/0x4000000000000002 softirq=8/8 fqs=5248 rcu: (t=21000 jiffies g=-1179 q=18) I tried rolling back just inits to. org help / color / mirror / Atom feed * [PATCH] rcu: Add cpu-exp indicator to expedited RCU CPU stall warnings @ 2022-05-18 11:43 Zqiang 2022-05-18 18:14 ` Paul E. o A CPU looping with preemption disabled. > > > > Fair enough, will take that approach! > > > > I am thinking in terms of something like the following: > > > > RCU_FLAVOR > > RCU_BH_FLAVOR > > RCU_SCHED. The kernel actually doesn't get to run on a CPU time within a certain timespan, either caused by timer not executed or different expectation of a timer speed. 1185519 – INFO: rcu_sched self-detected stall on CPU with nfsd Bug 1185519 - INFO: rcu_sched self-detected stall on CPU with nfsd Description Anthony Messina 2015-01-24 07:26:33 UTC Getting this kernel lockup on my NFS server, NFSv4. Add comments and normalize local variable name >> >> v1 --> v2: >> 1. In the vast majority of cases, real-time users face RCU stalls due to the delay of RCU callbacks execution. org help / color / mirror / Atom feed * [PATCH] rcu: Add cpu-exp indicator to expedited RCU CPU stall warnings @ 2022-05-18 11:43 Zqiang 2022-05-18 18:14 ` Paul E. Web. Throttle switch example. 4 ກ. o A bug in the RCU implementation. System logs: Jul 28 04:24:10 kernel: INFO: rcu_sched self-detected stall on CPU Jul 28 04:24:10 kernel: INFO: rcu_sched det. Resolve a git am conflict. Debugging rcu stalls. Web. A "grace period" must elapse between the two parts, and this grace period must be long enough that any readers. In this case, the printed information about current is not useful. Although a RCU Stall can be a side effect of a kernel BUG, this is not the typical case for the real-time kernel users. v5 --> v6: 1. Total pages: 1032661 [ 0. They have also tried applying: e97a32a5a3bc ("rcu: Do RCU GP kthread self-wakeup from softirq and interrupt") Any suggestions/help are appreciated. Image: haos_ova-7. The rcu_cpu_stall_suppress module parameter enables RCU's CPU stall. kd; tf. McKenney 0 siblings, 1 reply; 2+ messages in thread From: Zqiang @ 2022-05-18 11:43 UTC (permalink / raw) To: paulmck, frederic; +Cc: rcu, linux-kernel This commit adds a "D" indicator to expedited RCU. 9) and overlay2 after running for a few weeks. Update comments and document. Web. Using RCU’s CPU Stall Detector¶ This document first discusses what sorts of issues RCU’s CPU stall detector can locate, and then discusses kernel parameters and Kconfig options that can be used to fine-tune the detector’s operation. The kernel includes an RCU stall detection. Move the start point of statistics from rcu_stall_kick_kthreads() to rcu_implicit_dynticks_qs(), removing the dependency on irq_work. v5 --> v6: 1. 1185519 – INFO: rcu_sched self-detected stall on CPU with nfsd Bug 1185519 - INFO: rcu_sched self-detected stall on CPU with nfsd Description Anthony Messina 2015-01-24 07:26:33 UTC Getting this kernel lockup on my NFS server, NFSv4. In the vast majority of cases, real-time users face RCU stalls due to the delay of RCU callbacks execution. Update comments and document. Using RCU’s CPU Stall Detector. 123 with Imx6Q processor, we are getting rcu_preempt error and cpu hangs, The HW doesnt have HDMI or any on screen dispay, however the device had configurations and device tree for, GPU and HDMI enabled. Thanks to Elliott, Robert for the test. Add Kconfig option CONFIG_RCU_CPU_STALL_DEEP_DEBUG and boot parameter rcupdate. panic_on_rcu_stall parameter added to sysctl to debug RCU stalls on a vmcore. [ 29. The RCU callbacks are responsible for performing the necessary RCU work to achieve the end of a grace period. Expert 1446 points. Web. The issue occurrence is random but exists. Aligns the output of the last line of RCU stall. 979182] Modules linked in: nfsv3 nfs_acl mgc(OE) lustre(OE) lmv(OE) mdc(OE) fid(OE) osc(OE) lov(OE) fld(OE) ko2iblnd. Aligns the output of the last line of RCU stall. Nov 11, 2022 · 3. Web. [ 14. Fix the return type of kstat_cpu_irqs_sum () 2. Web. Resolve a git am conflict. 979162] NMI watchdog: BUG: soft lockup - CPU#26 stuck for 23s! [ptlrpcd_00_00:12056] [56376. panic_on_rcu_stall parameter added to sysctl to debug RCU stalls on a vmcore. Resolve a git am conflict. the in-band kernel may eventually complain about a RCU stall. Attached Logs for more information: [285165. The panic_on_rcu_stall interface is useful for defining the root cause of RCU stalls when using a vmcore. A third fix, which works only if this code does > >not use RCU and does not invoke any code that does use RCU, is to tell > >RCU that it should ignore this code (which will require a little work > >on RCU, as it currently does not tolerate this sort of thing aside from > >the idle threads). dampluos
Update comments and document. . Debugging rcu stalls
Change "rcu stall" to "RCU stall". Web. org help / color / mirror / Atom feed * [PATCH] rcu: Add cpu-exp indicator to expedited RCU CPU stall warnings @ 2022-05-18 11:43 Zqiang 2022-05-18 18:14 ` Paul E. 469541] 1-. de> wrote:. Although a RCU Stall can be a side effect of a kernel BUG, this is not the typical case for the real-time kernel users. Aligns the output of the last line of RCU stall. Booting with 38400bps, plus enabling CONFIG_RCU_FAST_NO_HZ and CONFIG_RCU_NOCB_CPU. Fix the return type of kstat_cpu_irqs_sum () > > 2. jl September 2,. LKML Archive on lore. For example, RCU stall warnings occurs in one hour while CPU idle>90%. and RCU per-CPU threads with FIFO 2 priority to avoid RCU stalls. When there are more than two continuous RCU stallings, correctly handle the value of the second and subsequent sampling periods. Add comments and normalize local variable name v1 --> v2: 1. Change "rcu stall" to "RCU stall". Image: haos_ova-7. For example, RCU stall warnings occurs in one hour while CPU idle>90%. When CPU idle<10%, RCU stall warnings occurs after >24hour. Re: [PATCH] rcu/performance: Fix kfree_perf_init() build warning on 32-bit kernels On Tue, May 26, 2020 at 08:27:44PM +0200, Ingo Molnar wrote: > * tip-bot2 for Joel Fernandes (Google) <tip-bot2@linutronix. This can prevent RCU's kthreads and softirq handlers from running. Solution Unverified - Updated December 2 2020 at 2:59 AM - English Issue Soft lockups and RCU sched CPU stalls are detected where many CPUs are looping in a spinlock. 979182] Modules linked in: nfsv3 nfs_acl mgc(OE) lustre(OE) lmv(OE) mdc(OE) fid(OE) osc(OE) lov(OE) fld(OE) ko2iblnd. 979182] Modules linked in: nfsv3 nfs_acl mgc(OE) lustre(OE) lmv(OE) mdc(OE) fid(OE) osc(OE) lov(OE) fld(OE) ko2iblnd. Fixed a bug in the code. This occurs due to the starvation of the rcuc/ threads, that runs with priority FIFO:2. A hard lockup is encountered and then the kernel crashes in the end. > > v4 --> v5: > 1. But my observation is that will be less to occur while lower CPU idle (CPU busy). When there are more than two continuous RCU stallings, correctly handle the value of the second and subsequent sampling periods. Although a RCU Stall can be a side effect of a kernel BUG, this is not the typical case for the real-time kernel users. Change "rcu stall" to "RCU stall". 14 ສ. 413319] (detected by 0, t=6302 jiffies, g=11405, c=11404, q=1880) [ 1144. 413319] (detected by 0, t=6302 jiffies, g=11405, c=11404, q=1880) [ 1144. org Bugzilla – Bug 207035 rcu: INFO: rcu_preempt self-detected stall on CPU Last modified: 2020-03-31 08:06:59 UTC. LKML Archive on lore. RCU stall warnings and hence system hangs after seeing crashes. This module parameter enables CPU stall detection by default, but may be overridden via boot-time parameter or at runtime via sysfs. The stalls are bad enough to cause hard drives to get kicked out of MD. Finally, this document explains the stall detector’s “splat” format. Web. No code change. This is quite unlikely, but has occurred at least once in real life. Update comments and document. 4844dec36bddb48 100644 > --- a/kernel/rcu/rcu. org help / color / mirror / Atom feed * [PATCH] rcu: Add cpu-exp indicator to expedited RCU CPU stall warnings @ 2022-05-18 11:43 Zqiang 2022-05-18 18:14 ` Paul E. This message will normally be followed by stack dumps for each CPU. v5 --> v6: 1. Using RCU’s CPU Stall Detector ¶. Note that certain high-overhead debugging options, for example the function_graph tracer, can result in interrupt handler taking considerably longer than normal, which can in turn result in RCU CPU stall warnings. LKML Archive on lore. Update comments and document. Add Kconfig option CONFIG_RCU_CPU_STALL_DEEP_DEBUG and boot parameter > rcupdate. McKenney 0 siblings, 1 reply; 2+ messages in thread From: Zqiang @ 2022-05-18 11:43 UTC (permalink / raw) To: paulmck, frederic; +Cc: rcu, linux-kernel This commit adds a "D" indicator to expedited RCU. says to use the RCU_CPU_STALL_TIMEOUT value converted from seconds to milliseconds. 3. The RCU callbacks are responsible for performing the necessary RCU work to achieve the end of a grace period. Booting with 38400bps, plus enabling CONFIG_RCU_FAST_NO_HZ and CONFIG_RCU_NOCB_CPU. Accelleration: VT-x/AMD-V, Nested Paging, KVM Paravirtualization. Although a RCU Stall can be a side effect of a kernel BUG, this is not the typical case for the real-time kernel users. v5 --> v6: 1. rcu_cpu_stall_suppress module parameter disables RCU’s CPU stall detector, which detects conditions that unduly delay RCU grace periods. is running at a higher priority than the RCU softirq threads. When Block Design added a AXI-DMA/AXI-VDMA IP core cause kernel startup reports “RCU: INFO: rcu_sched detected stalls on CPUs/tasks: ”. v5 --> v6: 1. In the vast majority of cases, real-time users face RCU stalls due to the delay of RCU callbacks execution. the in-band kernel may eventually complain about a RCU stall. org Subject: [PATCH AUTOSEL 5. v4 --> v5: 1. Add Kconfig option CONFIG_RCU_CPU_STALL_DEEP_DEBUG and boot parameter > rcupdate. Thanks to Elliott, Robert for the test. Web. Resolve a git am conflict. No code change. Web. LKML Archive on lore. Web. LKML Archive on lore. No code change. But it was not reproduced every time, about 1 time per 5-10 boots. It has NFS/SMB and MDADM installed. Attached Logs for more information: [285165. RCU stall warnings and hence system hangs after seeing crashes. In the process of debugging the RCU_preempt issue , I disabled the no used peripherals + HDMI and GPU, after disabling I am not seeing the RCU_preempt issue. Update comments and > document. Printk-debugging such timer issue requires enabling raw printk() . This document first discusses what sorts of issues RCU’s CPU stall detector can locate, and then discusses kernel parameters and Kconfig options that can be used to fine-tune the detector’s operation. Add Kconfig option CONFIG_RCU_CPU_STALL_DEEP_DEBUG and boot parameter rcupdate. Change "rcu stall" to "RCU stall". 5378 jiffies s: 69 root: 0x1/. For a 250 hz kernel a jiffi is 4 milliseconds, and for a 1000 hertz kernel a jiffi is 1 millisecond. We had tried many methods like remove drivers, run memtester, or make CPU busy. This added debugging information is suppressed by default and can be enabled by building the kernel with CONFIG_RCU_CPU_STALL_CPUTIME=y or by booting with rcupdate. 0: (1 GPs behind) idle=bf2/140000000000000/0 softirq=554/555 fqs=6754 (detected by 1, t=21003 jiffies, g=-154, c=-155, q=120339) Sending NMI from CPU 1 to CPUs 0:. 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