linux.git/kernel/rcu/Kconfig.debug, branch v6.6.132 Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git rcu: Allow up to five minutes expedited RCU CPU stall-warning timeouts 2023-01-09T20:09:52+00:00 Paul E. McKenney paulmck@kernel.org 2022-12-06T17:38:39+00:00 84ec7c20363f46a4031695eceb0374c1c4d6b9ec The maximum value of RCU CPU stall-warning timeouts has historically been five minutes (300 seconds). However, the recently introduced expedited RCU CPU stall-warning timeout is instead limited to 21 seconds. This causes problems for CI/fuzzing services such as syzkaller by obscuring the issue in question with expedited RCU CPU stall-warning timeout splats. This commit therefore sets the RCU_EXP_CPU_STALL_TIMEOUT Kconfig options upper bound to 300000 milliseconds, which is 300 seconds (AKA 5 minutes). [ paulmck: Apply feedback from Hillf Danton. ] [ paulmck: Apply feedback from Geert Uytterhoeven. ] Reported-by: Dave Chinner <david@fromorbit.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Tested-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
The maximum value of RCU CPU stall-warning timeouts has historically been
five minutes (300 seconds).  However, the recently introduced expedited
RCU CPU stall-warning timeout is instead limited to 21 seconds.  This
causes problems for CI/fuzzing services such as syzkaller by obscuring
the issue in question with expedited RCU CPU stall-warning timeout splats.

This commit therefore sets the RCU_EXP_CPU_STALL_TIMEOUT Kconfig options
upper bound to 300000 milliseconds, which is 300 seconds (AKA 5 minutes).

[ paulmck: Apply feedback from Hillf Danton. ]
[ paulmck: Apply feedback from Geert Uytterhoeven. ]

Reported-by: Dave Chinner <david@fromorbit.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
rcu: Add RCU stall diagnosis information 2023-01-05T20:21:11+00:00 Zhen Lei thunder.leizhen@huawei.com 2022-11-19T09:25:06+00:00 be42f00b73a0f50710d16eb7cb4efda0cce062dd Because RCU CPU stall warnings are driven from the scheduling-clock interrupt handler, a workload consisting of a very large number of short-duration hardware interrupts can result in misleading stall-warning messages. On systems supporting only a single level of interrupts, that is, where interrupts handlers cannot be interrupted, this can produce misleading diagnostics. The stack traces will show the innocent-bystander interrupted task, not the interrupts that are at the very least exacerbating the stall. This situation can be improved by displaying the number of interrupts and the CPU time that they have consumed. Diagnosing other types of stalls can be eased by also providing the count of softirqs and the CPU time that they consumed as well as the number of context switches and the task-level CPU time consumed. Consider the following output given this change: rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-....: (1250 ticks this GP) <omitted> rcu: hardirqs softirqs csw/system rcu: number: 624 45 0 rcu: cputime: 69 1 2425 ==> 2500(ms) This output shows that the number of hard and soft interrupts is small, there are no context switches, and the system takes up a lot of time. This indicates that the current task is looping with preemption disabled. The impact on system performance is negligible because snapshot is recorded only once for all continuous RCU stalls. 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.rcu_cpu_stall_cputime=1. Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
Because RCU CPU stall warnings are driven from the scheduling-clock
interrupt handler, a workload consisting of a very large number of
short-duration hardware interrupts can result in misleading stall-warning
messages.  On systems supporting only a single level of interrupts,
that is, where interrupts handlers cannot be interrupted, this can
produce misleading diagnostics.  The stack traces will show the
innocent-bystander interrupted task, not the interrupts that are
at the very least exacerbating the stall.

This situation can be improved by displaying the number of interrupts
and the CPU time that they have consumed.  Diagnosing other types
of stalls can be eased by also providing the count of softirqs and
the CPU time that they consumed as well as the number of context
switches and the task-level CPU time consumed.

Consider the following output given this change:

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu:     0-....: (1250 ticks this GP) <omitted>
rcu:          hardirqs   softirqs   csw/system
rcu:  number:      624         45            0
rcu: cputime:       69          1         2425   ==> 2500(ms)

This output shows that the number of hard and soft interrupts is small,
there are no context switches, and the system takes up a lot of time. This
indicates that the current task is looping with preemption disabled.

The impact on system performance is negligible because snapshot is
recorded only once for all continuous RCU stalls.

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.rcu_cpu_stall_cputime=1.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
rcu: Make SRCU mandatory 2022-11-29T23:00:06+00:00 Paul E. McKenney paulmck@kernel.org 2022-11-22T21:53:57+00:00 0cd7e350abc40eed5d3b60292dc102f700c88388 Kernels configured with CONFIG_PRINTK=n and CONFIG_SRCU=n get build failures. This causes trouble for deep embedded systems. But given that there are more than 25 instances of "select SRCU" in the kernel, it is hard to believe that there are many kernels running in production without SRCU. This commit therefore makes SRCU mandatory. The SRCU Kconfig option remains for backwards compatibility, and will be removed when it is no longer used. [ paulmck: Update per kernel test robot feedback. ] Reported-by: John Ogness <john.ogness@linutronix.de> Reported-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Cc: <linux-arch@vger.kernel.org> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested Reviewed-by: John Ogness <john.ogness@linutronix.de> 
Kernels configured with CONFIG_PRINTK=n and CONFIG_SRCU=n get build
failures.  This causes trouble for deep embedded systems.  But given
that there are more than 25 instances of "select SRCU" in the kernel,
it is hard to believe that there are many kernels running in production
without SRCU.  This commit therefore makes SRCU mandatory.  The SRCU
Kconfig option remains for backwards compatibility, and will be removed
when it is no longer used.

[ paulmck: Update per kernel test robot feedback. ]

Reported-by: John Ogness <john.ogness@linutronix.de>
Reported-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: <linux-arch@vger.kernel.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Merge tag 'char-misc-6.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc 2022-08-04T18:05:48+00:00 Linus Torvalds torvalds@linux-foundation.org 2022-08-04T18:05:48+00:00 228dfe98a313f6b6bff5da8b2c5e650e297ebf1a Pull char / misc driver updates from Greg KH: "Here is the large set of char and misc and other driver subsystem changes for 6.0-rc1. Highlights include: - large set of IIO driver updates, additions, and cleanups - new habanalabs device support added (loads of register maps much like GPUs have) - soundwire driver updates - phy driver updates - slimbus driver updates - tiny virt driver fixes and updates - misc driver fixes and updates - interconnect driver updates - hwtracing driver updates - fpga driver updates - extcon driver updates - firmware driver updates - counter driver update - mhi driver fixes and updates - binder driver fixes and updates - speakup driver fixes All of these have been in linux-next for a while without any reported problems" * tag 'char-misc-6.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (634 commits) drivers: lkdtm: fix clang -Wformat warning char: remove VR41XX related char driver misc: Mark MICROCODE_MINOR unused spmi: trace: fix stack-out-of-bound access in SPMI tracing functions dt-bindings: iio: adc: Add compatible for MT8188 iio: light: isl29028: Fix the warning in isl29028_remove() iio: accel: sca3300: Extend the trigger buffer from 16 to 32 bytes iio: fix iio_format_avail_range() printing for none IIO_VAL_INT iio: adc: max1027: unlock on error path in max1027_read_single_value() iio: proximity: sx9324: add empty line in front of bullet list iio: magnetometer: hmc5843: Remove duplicate 'the' iio: magn: yas530: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros iio: magnetometer: ak8974: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros iio: light: veml6030: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros iio: light: vcnl4035: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros iio: light: vcnl4000: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros iio: light: tsl2591: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() iio: light: tsl2583: Use DEFINE_RUNTIME_DEV_PM_OPS and pm_ptr() iio: light: isl29028: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() iio: light: gp2ap002: Switch to DEFINE_RUNTIME_DEV_PM_OPS and pm_ptr() ... 
Pull char / misc driver updates from Greg KH:
 "Here is the large set of char and misc and other driver subsystem
  changes for 6.0-rc1.

  Highlights include:

   - large set of IIO driver updates, additions, and cleanups

   - new habanalabs device support added (loads of register maps much
     like GPUs have)

   - soundwire driver updates

   - phy driver updates

   - slimbus driver updates

   - tiny virt driver fixes and updates

   - misc driver fixes and updates

   - interconnect driver updates

   - hwtracing driver updates

   - fpga driver updates

   - extcon driver updates

   - firmware driver updates

   - counter driver update

   - mhi driver fixes and updates

   - binder driver fixes and updates

   - speakup driver fixes

  All of these have been in linux-next for a while without any reported
  problems"

* tag 'char-misc-6.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (634 commits)
  drivers: lkdtm: fix clang -Wformat warning
  char: remove VR41XX related char driver
  misc: Mark MICROCODE_MINOR unused
  spmi: trace: fix stack-out-of-bound access in SPMI tracing functions
  dt-bindings: iio: adc: Add compatible for MT8188
  iio: light: isl29028: Fix the warning in isl29028_remove()
  iio: accel: sca3300: Extend the trigger buffer from 16 to 32 bytes
  iio: fix iio_format_avail_range() printing for none IIO_VAL_INT
  iio: adc: max1027: unlock on error path in max1027_read_single_value()
  iio: proximity: sx9324: add empty line in front of bullet list
  iio: magnetometer: hmc5843: Remove duplicate 'the'
  iio: magn: yas530: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros
  iio: magnetometer: ak8974: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros
  iio: light: veml6030: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros
  iio: light: vcnl4035: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros
  iio: light: vcnl4000: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr() macros
  iio: light: tsl2591: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr()
  iio: light: tsl2583: Use DEFINE_RUNTIME_DEV_PM_OPS and pm_ptr()
  iio: light: isl29028: Use DEFINE_RUNTIME_DEV_PM_OPS() and pm_ptr()
  iio: light: gp2ap002: Switch to DEFINE_RUNTIME_DEV_PM_OPS and pm_ptr()
  ...
rcu: Forbid RCU_STRICT_GRACE_PERIOD in TINY_RCU kernels 2022-07-19T18:39:59+00:00 Paul E. McKenney paulmck@kernel.org 2022-05-18T01:03:36+00:00 b3ade95b8ee507d650d9e163abfdf645a9f3886d The RCU_STRICT_GRACE_PERIOD Kconfig option does nothing in kernels built with CONFIG_TINY_RCU=y, so this commit adjusts the dependencies to disallow this combination. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com> 
The RCU_STRICT_GRACE_PERIOD Kconfig option does nothing in kernels
built with CONFIG_TINY_RCU=y, so this commit adjusts the dependencies
to disallow this combination.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
remove CONFIG_ANDROID 2022-07-01T08:41:09+00:00 Christoph Hellwig hch@lst.de 2022-06-29T15:01:02+00:00 1045a06724f322ed61f1ffb994427c7bdbe64647 The ANDROID config symbol is only used to guard the binder config symbol and to inject completely random config changes. Remove it as it is obviously a bad idea. Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220629150102.1582425-2-hch@lst.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
The ANDROID config symbol is only used to guard the binder config
symbol and to inject completely random config changes.  Remove it
as it is obviously a bad idea.

Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220629150102.1582425-2-hch@lst.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Merge branch 'exp.2022.05.11a' into HEAD 2022-05-11T18:49:35+00:00 Paul E. McKenney paulmck@kernel.org 2022-05-11T18:49:35+00:00 ce13389053a347aa9f8ffbfda2238352536e15c9 exp.2022.05.11a: Expedited-grace-period latency-reduction updates. 
exp.2022.05.11a: Expedited-grace-period latency-reduction updates.
rcu: Introduce CONFIG_RCU_EXP_CPU_STALL_TIMEOUT 2022-05-11T18:38:50+00:00 Uladzislau Rezki uladzislau.rezki@sony.com 2022-02-16T13:52:09+00:00 28b3ae426598e722cf5d5ab9cc7038791b955a56 Currently both expedited and regular grace period stall warnings use a single timeout value that with units of seconds. However, recent Android use cases problem require a sub-100-millisecond expedited RCU CPU stall warning. Given that expedited RCU grace periods normally complete in far less than a single millisecond, especially for small systems, this is not unreasonable. Therefore introduce the CONFIG_RCU_EXP_CPU_STALL_TIMEOUT kernel configuration that defaults to 20 msec on Android and remains the same as that of the non-expedited stall warnings otherwise. It also can be changed in run-time via: /sys/.../parameters/rcu_exp_cpu_stall_timeout. [ paulmck: Default of zero to use CONFIG_RCU_STALL_TIMEOUT. ] Signed-off-by: Uladzislau Rezki <uladzislau.rezki@sony.com> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
Currently both expedited and regular grace period stall warnings use
a single timeout value that with units of seconds.  However, recent
Android use cases problem require a sub-100-millisecond expedited RCU CPU
stall warning.  Given that expedited RCU grace periods normally complete
in far less than a single millisecond, especially for small systems,
this is not unreasonable.

Therefore introduce the CONFIG_RCU_EXP_CPU_STALL_TIMEOUT kernel
configuration that defaults to 20 msec on Android and remains the same
as that of the non-expedited stall warnings otherwise.  It also can be
changed in run-time via: /sys/.../parameters/rcu_exp_cpu_stall_timeout.

[ paulmck: Default of zero to use CONFIG_RCU_STALL_TIMEOUT. ]

Signed-off-by: Uladzislau Rezki <uladzislau.rezki@sony.com>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
rcuscale: Allow rcuscale without RCU Tasks Rude/Trace 2022-04-20T23:53:19+00:00 Paul E. McKenney paulmck@kernel.org 2022-03-26T00:05:40+00:00 5ce027f4cd0e2f28ea5574ede9eef290e2ede5c5 Currently, a CONFIG_PREEMPT_NONE=y kernel substitutes normal RCU for RCU Tasks Rude and RCU Tasks Trace. Unless that kernel builds rcuscale, whether built-in or as a module, in which case these RCU Tasks flavors are (unnecessarily) built in. This both increases kernel size and increases the complexity of certain tracing operations. This commit therefore decouples the presence of rcuscale from the presence of RCU Tasks Rude and RCU Tasks Trace. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
Currently, a CONFIG_PREEMPT_NONE=y kernel substitutes normal RCU for
RCU Tasks Rude and RCU Tasks Trace.  Unless that kernel builds rcuscale,
whether built-in or as a module, in which case these RCU Tasks flavors are
(unnecessarily) built in.  This both increases kernel size and increases
the complexity of certain tracing operations.  This commit therefore
decouples the presence of rcuscale from the presence of RCU Tasks Rude
and RCU Tasks Trace.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
rcuscale: Allow rcuscale without RCU Tasks 2022-04-20T23:53:19+00:00 Paul E. McKenney paulmck@kernel.org 2022-03-25T23:39:01+00:00 4df002d908796c1ff87b985af1d31a0e36e6c66f Currently, a CONFIG_PREEMPT_NONE=y kernel substitutes normal RCU for RCU Tasks. Unless that kernel builds rcuscale, whether built-in or as a module, in which case RCU Tasks is (unnecessarily) built. This both increases kernel size and increases the complexity of certain tracing operations. This commit therefore decouples the presence of rcuscale from the presence of RCU Tasks. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
Currently, a CONFIG_PREEMPT_NONE=y kernel substitutes normal RCU for
RCU Tasks.  Unless that kernel builds rcuscale, whether built-in or as
a module, in which case RCU Tasks is (unnecessarily) built.  This both
increases kernel size and increases the complexity of certain tracing
operations.  This commit therefore decouples the presence of rcuscale
from the presence of RCU Tasks.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>