The rcu_user_enter_after_irq() and rcu_user_exit_after_irq()
functions were intended for use by adaptive ticks, but changes
in implementation have rendered them unnecessary. This commit
therefore removes them.
Reported-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Currently, RCU tracepoints save only a pointer to strings in the
ring buffer. When displayed via the /sys/kernel/debug/tracing/trace file
they are referenced like the printf "%s" that looks at the address
in the ring buffer and prints out the string it points too. This requires
that the strings are constant and persistent in the kernel.
The problem with this is for tools like trace-cmd and perf that read the
binary data from the buffers but have no access to the kernel memory to
find out what string is represented by the address in the buffer.
By using the tracepoint_string infrastructure, the RCU tracepoint strings
can be exported such that userspace tools can map the addresses to
the strings.
# cat /sys/kernel/debug/tracing/printk_formats
0xffffffff81a4a0e8 : "rcu_preempt"
0xffffffff81a4a0f4 : "rcu_bh"
0xffffffff81a4a100 : "rcu_sched"
0xffffffff818437a0 : "cpuqs"
0xffffffff818437a6 : "rcu_sched"
0xffffffff818437a0 : "cpuqs"
0xffffffff818437b0 : "rcu_bh"
0xffffffff818437b7 : "Start context switch"
0xffffffff818437cc : "End context switch"
0xffffffff818437a0 : "cpuqs"
[...]
Now userspaces tools can display:
rcu_utilization: Start context switch
rcu_dyntick: Start 1 0
rcu_utilization: End context switch
rcu_batch_start: rcu_preempt CBs=0/5 bl=10
rcu_dyntick: End 0 140000000000000
rcu_invoke_callback: rcu_preempt rhp=0xffff880071c0d600 func=proc_i_callback
rcu_invoke_callback: rcu_preempt rhp=0xffff880077b5b230 func=__d_free
rcu_dyntick: Start 140000000000000 0
rcu_invoke_callback: rcu_preempt rhp=0xffff880077563980 func=file_free_rcu
rcu_batch_end: rcu_preempt CBs-invoked=3 idle=>c<>c<>c<>c<
rcu_utilization: End RCU core
rcu_grace_period: rcu_preempt 9741 start
rcu_dyntick: Start 1 0
rcu_dyntick: End 0 140000000000000
rcu_dyntick: Start 140000000000000 0
Instead of:
rcu_utilization: ffffffff81843110
rcu_future_grace_period: ffffffff81842f1d 9939 9939 9940 0 0 3 ffffffff81842f32
rcu_batch_start: ffffffff81842f1d CBs=0/4 bl=10
rcu_future_grace_period: ffffffff81842f1d 9939 9939 9940 0 0 3 ffffffff81842f3c
rcu_grace_period: ffffffff81842f1d 9939 ffffffff81842f80
rcu_invoke_callback: ffffffff81842f1d rhp=0xffff88007888aac0 func=file_free_rcu
rcu_grace_period: ffffffff81842f1d 9939 ffffffff81842f95
rcu_invoke_callback: ffffffff81842f1d rhp=0xffff88006aeb4600 func=proc_i_callback
rcu_future_grace_period: ffffffff81842f1d 9939 9939 9940 0 0 3 ffffffff81842f32
rcu_future_grace_period: ffffffff81842f1d 9939 9939 9940 0 0 3 ffffffff81842f3c
rcu_invoke_callback: ffffffff81842f1d rhp=0xffff880071cb9fc0 func=__d_free
rcu_grace_period: ffffffff81842f1d 9939 ffffffff81842f80
rcu_invoke_callback: ffffffff81842f1d rhp=0xffff88007888ae80 func=file_free_rcu
rcu_batch_end: ffffffff81842f1d CBs-invoked=4 idle=>c<>c<>c<>c<
rcu_utilization: ffffffff8184311f
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The RCU_STATE_INITIALIZER() macro is used only in the rcutree.c file
as well as the rcutree_plugin.h file. It is passed as a rvalue to
a variable of a similar name. A per_cpu variable is also created
with a similar name as well.
The uses of RCU_STATE_INITIALIZER() can be simplified to remove some
of the duplicate code that is done. Currently the three users of this
macro has this format:
struct rcu_state rcu_sched_state =
RCU_STATE_INITIALIZER(rcu_sched, call_rcu_sched);
DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
Notice that "rcu_sched" is called three times. This is the same with
the other two users. This can be condensed to just:
RCU_STATE_INITIALIZER(rcu_sched, call_rcu_sched);
by moving the rest into the macro itself.
This also opens the door to allow the RCU tracepoint strings and
their addresses to be exported so that userspace tracing tools can
translate the contents of the pointers of the RCU tracepoints.
The change will allow for helper code to be placed in the
RCU_STATE_INITIALIZER() macro to export the name that is used.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
All the RCU tracepoints and functions that reference char pointers do
so with just 'char *' even though they do not modify the contents of
the string itself. This will cause warnings if a const char * is used
in one of these functions.
The RCU tracepoints store the pointer to the string to refer back to them
when the trace output is displayed. As this can be minutes, hours or
even days later, those strings had better be constant.
This change also opens the door to allow the RCU tracepoint strings and
their addresses to be exported so that userspace tracing tools can
translate the contents of the pointers of the RCU tracepoints.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The __cpuinit type of throwaway sections might have made sense
some time ago when RAM was more constrained, but now the savings
do not offset the cost and complications. For example, the fix in
commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time")
is a good example of the nasty type of bugs that can be created
with improper use of the various __init prefixes.
After a discussion on LKML[1] it was decided that cpuinit should go
the way of devinit and be phased out. Once all the users are gone,
we can then finally remove the macros themselves from linux/init.h.
This removes all the drivers/rcu uses of the __cpuinit macros
from all C files.
[1] https://lkml.org/lkml/2013/5/20/589
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@freedesktop.org>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Calling kthread_run with a single name parameter causes it to be handled
as a format string. Many callers are passing potentially dynamic string
content, so use "%s" in those cases to avoid any potential accidents.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Systems with HZ=100 can have slow bootup times due to the default
three-jiffy delays between quiescent-state forcing attempts. This
commit therefore auto-tunes the RCU_JIFFIES_TILL_FORCE_QS value based
on the value of HZ. However, this would break very large systems that
require more time between quiescent-state forcing attempts. This
commit therefore also ups the default delay by one jiffy for each
256 CPUs that might be on the system (based off of nr_cpu_ids at
runtime, -not- NR_CPUS at build time).
Updated to collapse #ifdefs for RCU_JIFFIES_TILL_FORCE_QS into a
step-function definition as suggested by Josh Triplett.
Reported-by: Paul Mackerras <paulus@au1.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The __rcu_process_callbacks() invokes note_gp_changes() immediately
before invoking rcu_check_quiescent_state(), which conditionally
invokes that same function. This commit therefore eliminates the
call to note_gp_changes() in __rcu_process_callbacks() in favor of
making unconditional to call from rcu_check_quiescent_state() to
note_gp_changes().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Given the changes that introduce note_gp_change(), rcu_start_gp_per_cpu()
is now a trivial wrapper function with only one caller. This commit
therefore inlines it into its sole call site.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
One of the calls to check_for_new_grace_period() is now redundant due to
an immediately preceding call to note_gp_changes(). Eliminating this
redundant call leaves a single caller, which is simpler if inlined.
This commit therefore eliminates the redundant call and inlines the
body of check_for_new_grace_period() into the single remaining call site.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit eliminates some duplicated code by merging
__rcu_process_gp_end() into __note_gp_changes().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Because note_gp_changes() now incorporates rcu_process_gp_end() function,
this commit switches to the former and eliminates the latter. In
addition, this commit changes external calls from __rcu_process_gp_end()
to __note_gp_changes().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Because note_new_gpnum() now also checks for the ends of old grace periods,
this commit changes its name to note_gp_changes(). Later commits will merge
rcu_process_gp_end() into note_gp_changes().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The current implementation can detect the beginning of a new grace period
before noting the end of a previous grace period. Although the current
implementation correctly handles this sort of nonsense, it would be
good to reduce RCU's state space by making such nonsense unnecessary,
which is now possible thanks to the fact that RCU's callback groups are
now numbered.
This commit therefore makes __note_new_gpnum() invoke
__rcu_process_gp_end() in order to note the ends of prior grace
periods before noting the beginnings of new grace periods.
Of course, this now means that note_new_gpnum() notes both the
beginnings and ends of grace periods, and could therefore be
used in place of rcu_process_gp_end(). But that is a job for
later commits.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The addition of callback numbering allows combining the detection of the
ends of old grace periods and the beginnings of new grace periods. This
commit moves code to set the stage for this combining.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The full dynticks tree needs the latest RCU and sched
upstream updates in order to fix some dependencies.
Merge a common upstream merge point that has these
updates.
Conflicts:
include/linux/perf_event.h
kernel/rcutree.h
kernel/rcutree_plugin.h
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Pull RCU updates from Ingo Molnar:
"The main changes in this cycle are mostly related to preparatory work
for the full-dynticks work:
- Remove restrictions on no-CBs CPUs, make RCU_FAST_NO_HZ take
advantage of numbered callbacks, do callback accelerations based on
numbered callbacks. Posted to LKML at
https://lkml.org/lkml/2013/3/18/960
- RCU documentation updates. Posted to LKML at
https://lkml.org/lkml/2013/3/18/570
- Miscellaneous fixes. Posted to LKML at
https://lkml.org/lkml/2013/3/18/594"
* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
rcu: Make rcu_accelerate_cbs() note need for future grace periods
rcu: Abstract rcu_start_future_gp() from rcu_nocb_wait_gp()
rcu: Rename n_nocb_gp_requests to need_future_gp
rcu: Push lock release to rcu_start_gp()'s callers
rcu: Repurpose no-CBs event tracing to future-GP events
rcu: Rearrange locking in rcu_start_gp()
rcu: Make RCU_FAST_NO_HZ take advantage of numbered callbacks
rcu: Accelerate RCU callbacks at grace-period end
rcu: Export RCU_FAST_NO_HZ parameters to sysfs
rcu: Distinguish "rcuo" kthreads by RCU flavor
rcu: Add event tracing for no-CBs CPUs' grace periods
rcu: Add event tracing for no-CBs CPUs' callback registration
rcu: Introduce proper blocking to no-CBs kthreads GP waits
rcu: Provide compile-time control for no-CBs CPUs
rcu: Tone down debugging during boot-up and shutdown.
rcu: Add softirq-stall indications to stall-warning messages
rcu: Documentation update
rcu: Make bugginess of code sample more evident
rcu: Fix hlist_bl_set_first_rcu() annotation
rcu: Delete unused rcu_node "wakemask" field
...
Adaptive-ticks CPUs inform RCU when they enter kernel mode, but they do
not necessarily turn the scheduler-clock tick back on. This state of
affairs could result in RCU waiting on an adaptive-ticks CPU running
for an extended period in kernel mode. Such a CPU will never run the
RCU state machine, and could therefore indefinitely extend the RCU state
machine, sooner or later resulting in an OOM condition.
This patch, inspired by an earlier patch by Frederic Weisbecker, therefore
causes RCU's force-quiescent-state processing to check for this condition
and to send an IPI to CPUs that remain in that state for too long.
"Too long" currently means about three jiffies by default, which is
quite some time for a CPU to remain in the kernel without blocking.
The rcu_tree.jiffies_till_first_fqs and rcutree.jiffies_till_next_fqs
sysfs variables may be used to tune "too long" if needed.
Reported-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
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.
Paul E. McKenney
Steven Rostedt (Red Hat)
Paul Gortmaker
Kees Cook
Frederic Weisbecker
Linus Torvalds
Akinobu Mita