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Merge branches 'doc.2013.03.12a', 'fixes.2013.03.13a' and 'idlenocb.2013.03.26b' into HEAD

Browse source 
doc.2013.03.12a: Documentation changes.

fixes.2013.03.13a: Miscellaneous fixes.

idlenocb.2013.03.26b: Remove restrictions on no-CBs CPUs, make
	RCU_FAST_NO_HZ take advantage of numbered callbacks, add
	callback acceleration based on numbered callbacks.
This commit is contained in:
Paul E. McKenney 2013-03-26 08:07:38 -07:00
commit 6d87669357
11 changed files with 603 additions and 505 deletions
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33
Documentation/RCU/stallwarn.txt
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@ -92,14 +92,14 @@ If the CONFIG_RCU_CPU_STALL_INFO kernel configuration parameter is set,
more information is printed with the stall-warning message, for example:
INFO: rcu_preempt detected stall on CPU
0: (63959 ticks this GP) idle=241/3fffffffffffffff/0
0: (63959 ticks this GP) idle=241/3fffffffffffffff/0 softirq=82/543
(t=65000 jiffies)
In kernels with CONFIG_RCU_FAST_NO_HZ, even more information is
printed:
INFO: rcu_preempt detected stall on CPU
0: (64628 ticks this GP) idle=dd5/3fffffffffffffff/0 drain=0 . timer not pending
0: (64628 ticks this GP) idle=dd5/3fffffffffffffff/0 softirq=82/543 last_accelerate: a345/d342 nonlazy_posted: 25 .D
(t=65000 jiffies)
The "(64628 ticks this GP)" indicates that this CPU has taken more
@ -116,13 +116,28 @@ number between the two "/"s is the value of the nesting, which will
be a small positive number if in the idle loop and a very large positive
number (as shown above) otherwise.
For CONFIG_RCU_FAST_NO_HZ kernels, the "drain=0" indicates that the CPU is
not in the process of trying to force itself into dyntick-idle state, the
"." indicates that the CPU has not given up forcing RCU into dyntick-idle
mode (it would be "H" otherwise), and the "timer not pending" indicates
that the CPU has not recently forced RCU into dyntick-idle mode (it
would otherwise indicate the number of microseconds remaining in this
forced state).
The "softirq=" portion of the message tracks the number of RCU softirq
handlers that the stalled CPU has executed. The number before the "/"
is the number that had executed since boot at the time that this CPU
last noted the beginning of a grace period, which might be the current
(stalled) grace period, or it might be some earlier grace period (for
example, if the CPU might have been in dyntick-idle mode for an extended
time period. The number after the "/" is the number that have executed
since boot until the current time. If this latter number stays constant
across repeated stall-warning messages, it is possible that RCU's softirq
handlers are no longer able to execute on this CPU. This can happen if
the stalled CPU is spinning with interrupts are disabled, or, in -rt
kernels, if a high-priority process is starving RCU's softirq handler.
For CONFIG_RCU_FAST_NO_HZ kernels, the "last_accelerate:" prints the
low-order 16 bits (in hex) of the jiffies counter when this CPU last
invoked rcu_try_advance_all_cbs() from rcu_needs_cpu() or last invoked
rcu_accelerate_cbs() from rcu_prepare_for_idle(). The "nonlazy_posted:"
prints the number of non-lazy callbacks posted since the last call to
rcu_needs_cpu(). Finally, an "L" indicates that there are currently
no non-lazy callbacks ("." is printed otherwise, as shown above) and
"D" indicates that dyntick-idle processing is enabled ("." is printed
otherwise, for example, if disabled via the "nohz=" kernel boot parameter).
Multiple Warnings From One Stall