| Age | Commit message (Collapse) | Author |
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The ->dynticks_nmi_nesting field records the nesting depth of both
interrupt and NMI handlers. Because the kernel can enter interrupts
and never leave them (and vice versa) and because NMIs can interrupt
manipulation of the ->dynticks_nmi_nesting field, the values in this
field must be both chosen and maniupated very carefully. As a result,
although the value is zero when the corresponding CPU is executing
neither an interrupt nor an NMI handler, it is 4,611,686,018,427,387,906
on 64-bit systems when there is a single level of interrupt/NMI handling
in progress.
This number is difficult to remember and interpret, so this commit
switches the output to hexadecimal, resulting in the much nicer
0x4000000000000002.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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One danger of using __maybe_unused is that the compiler doesn't yell
at you when you remove the last reference, witness rcu_bind_gp_kthread()
and its local variable "cpu". This commit removes this local variable.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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The rcu_kick_nohz_cpu() function is no longer used, and the functionality
it used to provide is now provided by a call to resched_cpu() in the
force-quiescent-state function rcu_implicit_dynticks_qs(). This commit
therefore removes rcu_kick_nohz_cpu().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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The rcu_preempt_qs() function only applies to the CPU, not the task.
A task really is allowed to invoke this function while in an RCU-preempt
read-side critical section, but only if it has first added itself to
some leaf rcu_node structure's ->blkd_tasks list.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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If any scheduling-clock interrupt interrupts an RCU-preempt read-side
critical section, the interrupted task's ->rcu_read_unlock_special.b.need_qs
field is set. This causes the outermost rcu_read_unlock() to incur the
extra overhead of calling into rcu_read_unlock_special(). This commit
reduces that overhead by setting ->rcu_read_unlock_special.b.need_qs only
if the grace period has been in effect for more than one second.
Why one second? Because this is comfortably smaller than the minimum
RCU CPU stall-warning timeout of three seconds, but long enough that the
.need_qs marking should happen quite rarely. And if your RCU read-side
critical section has run on-CPU for a full second, it is not unreasonable
to invest some CPU time in ending the grace period quickly.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit also adjusts some whitespace while in the area.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Revert string-breaking %s as requested by Andy Shevchenko. ]
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Because rcu_read_unlock_special() is no longer used outside of
kernel/rcu/tree_plugin.h, this commit makes it static.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Interactions between CPU-hotplug operations and grace-period
initialization can result in dump_blkd_tasks(). One of the first
debugging actions in this case is to search back in dmesg to work
out which of the affected rcu_node structure's CPUs are online and to
determine the last CPU-hotplug operation affecting any of those CPUs.
This can be laborious and error-prone, especially when console output
is lost.
This commit therefore causes dump_blkd_tasks() to dump the state of
the affected rcu_node structure's CPUs and the last grace period during
which the last offline and online operation affected each of these CPUs.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit updates dump_blkd_tasks() to print out quiescent-state
bitmasks for the rcu_node structures further up the tree. This
information helps debugging of interactions between CPU-hotplug
operations and RCU grace-period initialization.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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RCU should only be waiting on CPUs that were online at the time that the
current grace period started. Failure to abide by this rule can result
in confusing splats during grace-period cleanup and initialization.
This commit therefore adds a check to RCU-preempt's preempted-task
queuing that checks for waiting on newly onlined CPUs.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Consider the following sequence of events in a PREEMPT=y kernel:
1. All CPUs corresponding to a given leaf rcu_node structure are
offline.
2. The first phase of the rcu_gp_init() function's grace-period
initialization runs, and sets that rcu_node structure's
->qsmaskinit to zero, as it should.
3. One of the CPUs corresponding to that rcu_node structure comes
back online. Note that because this CPU came online after the
grace period started, this grace period can safely ignore this
newly onlined CPU.
4. A task running on the newly onlined CPU enters an RCU-preempt
read-side critical section, and is then preempted. Because
the corresponding rcu_node structure's ->qsmask is zero,
rcu_preempt_ctxt_queue() leaves the rcu_node structure's
->gp_tasks field NULL, as it should.
5. The rcu_gp_init() function continues running the second phase of
grace-period initialization. The ->qsmask field of the parent of
the aforementioned leaf rcu_node structure is set to not expect
a quiescent state from the leaf, as is only right and proper.
However, when rcu_gp_init() reaches the leaf, it invokes
rcu_preempt_check_blocked_tasks(), which sees that the leaf's
->blkd_tasks list is non-empty, and therefore sets the leaf's
->gp_tasks field to reference the first task on that list.
6. The grace period ends before the preempted task resumes, which
is perfectly fine, given that this grace period was under no
obligation to wait for that task to exit its late-starting
RCU-preempt read-side critical section. Unfortunately, the
leaf's ->gp_tasks field is non-NULL, so rcu_gp_cleanup() splats.
After all, it appears to rcu_gp_cleanup() that the grace period
failed to wait for a task that was supposed to be blocking that
grace period.
This commit avoids this false-positive splat by adding a check of both
->qsmaskinit and ->wait_blkd_tasks to rcu_preempt_check_blocked_tasks().
If both ->qsmaskinit and ->wait_blkd_tasks are zero, then the task must
have entered its RCU-preempt read-side critical section late (after all,
the CPU that it is running on was not online at that time), which means
that the upper-level rcu_node structure won't be waiting for anything
on the leaf anyway.
If ->wait_blkd_tasks is non-zero, then there is at least one task on
ths rcu_node structure's ->blkd_tasks list whose RCU read-side
critical section predates the current grace period. If ->qsmaskinit
is non-zero, there is at least one CPU that was online at the start
of the current grace period. Thus, if both are zero, there is nothing
to wait for.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit fixes a typo and adds some additional debugging to the
message emitted when a task blocking the current grace period is listed
as blocking it when either that grace period ends or the next grace
period begins. This commit also reformats the console message for
readability.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Now that everything has been converted to use ->gp_seq instead of
->gpnum and ->completed, this commit removes ->gpnum and ->completed.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit makes the rcu_quiescent_state_report tracepoint use ->gp_seq
instead of ->gpnum.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit makes the rcu_unlock_preempted_task tracepoint use ->gp_seq
instead of ->gpnum.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit makes the rcu_preempt_task tracepoint use ->gp_seq instead
of ->gpnum.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit makes the rcu_grace_period tracepoint use gp_seq instead
of ->gpnum or ->completed. It also introduces a "cpuofl-bgp" string to
less obscurely indicate when a CPU has gone offline while a grace period
is waiting on it.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit makes rcu_nocb_wait_gp() check rdp->gp_seq_needed to see
if the current CPU already knows about the needed grace period having
already been requested. If so, it avoids acquiring the corresponding
leaf rcu_node structure's ->lock, thus decreasing contention. This
optimization is intended for cases where either multiple leader rcuo
kthreads are running on the same CPU or these kthreads are running on
a non-offloaded (e.g., housekeeping) CPU.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Move lock release past "if" as suggested by Joel Fernandes. ]
[ paulmck: Fix caching of furthest-future requested grace period. ]
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This commit makes the RCU CPU stall-warning code in print_other_cpu_stall(),
print_cpu_stall(), and check_cpu_stall() use ->gp_seq instead of ->gpnum
and ->completed.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit converts the grace-period request code paths from ->completed
and ->gpnum to ->gp_seq. The need_future_gp_element() macro encapsulates
the shift operation required to use ->gp_seq as an index to the
->need_future_gp[] array. The rcu_cbs_completed() function is removed
in favor of the rcu_seq_snap() function. The rcu_start_this_gp()
gets some temporary consistency checks and uses rcu_seq_done(),
rcu_seq_current(), rcu_seq_state(), and rcu_gp_in_progress() in place
of the earlier open-coded comparisons of ->gpnum and ->completed.
The rcu_future_gp_cleanup() function replaces use of ->completed
with ->gp_seq. The rcu_accelerate_cbs() function replaces a call to
rcu_cbs_completed() with one to rcu_seq_snap(). The rcu_advance_cbs()
function replaces an access to >completed with one to ->gp_seq and adds
some temporary warnings. The rcu_nocb_wait_gp() function replaces a
call to rcu_cbs_completed() with one to rcu_seq_snap() and an open-coded
comparison with rcu_seq_done().
The temporary warnings will be removed when the various ->gpnum and
->completed fields are removed. Their purpose is to locate code who
might still be using ->gpnum and ->completed. (Much easier that way
than trying to trace down the causes of too-short grace periods and
grace-period hangs!)
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit switches the quiescent-state no-backtracking checks from
->gpnum and ->completed to ->gp_seq.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit switches the interrupt-disabled detection mechanism to
->gp_seq. This mechanism is used as part of RCU CPU stall warnings,
and detects cases where the stall is due to a CPU having interrupts
disabled.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit makes rcu_try_advance_all_cbs() use ->gp_seq. It uses
rcu_seq_ctr() in order to shift away the state bits, so that the
low-order bits of the result may safely be used to index ->nocb_gp_wq[].
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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This commit makes rcu_try_advance_all_cbs() use ->gp_seq, with the
exception of tracing, which will be converted later.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Sparse reported this:
| kernel/rcu/tree_plugin.h:814:9: warning: incorrect type in argument 1 (different modifiers)
| kernel/rcu/tree_plugin.h:814:9: expected struct lockdep_map const *lock
| kernel/rcu/tree_plugin.h:814:9: got struct lockdep_map [noderef] *<noident>
This is caused by using vanilla lockdep annotations on rcu_node::lock,
and that requires accessing ->lock of rcu_node directly. However we need
to keep rcu_node::lock __private to avoid breaking its extra ordering
guarantee. And we have a dedicated lockdep annotation for
rcu_node::lock, so use it.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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The WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp()) in
rcu_gp_cleanup() triggers (inexplicably, of course) every so often.
This commit therefore extracts more information.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Since swait basically implemented exclusive waits only, make sure
the API reflects that.
$ git grep -l -e "\<swake_up\>"
-e "\<swait_event[^ (]*"
-e "\<prepare_to_swait\>" | while read file;
do
sed -i -e 's/\<swake_up\>/&_one/g'
-e 's/\<swait_event[^ (]*/&_exclusive/g'
-e 's/\<prepare_to_swait\>/&_exclusive/g' $file;
done
With a few manual touch-ups.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: bigeasy@linutronix.de
Cc: oleg@redhat.com
Cc: paulmck@linux.vnet.ibm.com
Cc: pbonzini@redhat.com
Link: https://lkml.kernel.org/r/20180612083909.261946548@infradead.org
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and 'torture.2018.05.15a' into HEAD
exp.2018.05.15a: Parallelize expedited grace-period initialization.
fixes.2018.05.15a: Miscellaneous fixes.
lock.2018.05.15a: Decrease lock contention on root rcu_node structure,
which is a step towards merging RCU flavors.
torture.2018.05.15a: Torture-test updates.
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The rcu_accelerate_cbs() function selects a grace-period target, which
it uses to have rcu_segcblist_accelerate() assign numbers to recently
queued callbacks. Then it invokes rcu_start_future_gp(), which selects
a grace-period target again, which is a bit pointless. This commit
therefore changes rcu_start_future_gp() to take the grace-period target as
a parameter, thus avoiding double selection. This commit also changes
the name of rcu_start_future_gp() to rcu_start_this_gp() to reflect
this change in functionality, and also makes a similar change to the
name of trace_rcu_future_gp().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
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Currently, rcu_gp_cleanup() scans the rcu_node tree in order to reset
state to reflect the end of the grace period. It also checks to see
whether a new grace period is needed, but in a number of cases, rather
than directly cause the new grace period to be immediately started, it
instead leaves the grace-period-needed state where various fail-safes
can find it. This works fine, but results in higher contention on the
root rcu_node structure's ->lock, which is undesirable, and contention
on that lock has recently become noticeable.
This commit therefore makes rcu_gp_cleanup() immediately start a new
grace period if there is any need for one.
It is quite possible that it will later be necessary to throttle the
grace-period rate, but that can be dealt with when and if.
Reported-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
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Accessors for the ->need_future_gp[] array are currently open-coded,
which makes them difficult to change. To improve maintainability, this
commit adds need_future_gp_mask() to compute the indexing mask from the
array size, need_future_gp_element() to access the element corresponding
to the specified grace-period number, and need_any_future_gp() to
determine if any future grace period is needed. This commit also applies
need_future_gp_element() to existing open-coded single-element accesses.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
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This commit adds rcu_first_leaf_node() that returns a pointer to
the first leaf rcu_node structure in the specified RCU flavor and an
rcu_is_leaf_node() that returns true iff the specified rcu_node structure
is a leaf. This commit also uses these macros where appropriate.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
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The header comment for rcu_bind_gp_kthread() refers to sysidle, which
is no longer with us. However, it is still important to bind RCU's
grace-period kthreads to the housekeeping CPU(s), so rather than remove
rcu_bind_gp_kthread(), this commit updates the comment.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
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The __rcu_read_lock() and __rcu_read_unlock() functions were moved
to kernel/rcu/update.c in order to implement tiny preemptible RCU.
However, tiny preemptible RCU was removed from the kernel a long time
ago, so this commit belatedly moves them back into the only remaining
preemptible-RCU code.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
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Commit e31d28b6ab8f ("trace: Eliminate cond_resched_rcu_qs() in favor
of cond_resched()") substituted cond_resched() for the earlier call
to cond_resched_rcu_qs(). However, the new-age cond_resched() does
not do anything to help RCU-tasks grace periods because (1) RCU-tasks
is only enabled when CONFIG_PREEMPT=y and (2) cond_resched() is a
complete no-op when preemption is enabled. This situation results
in hangs when running the trace benchmarks.
A number of potential fixes were discussed on LKML
(https://lkml.kernel.org/r/20180224151240.0d63a059@vmware.local.home),
including making cond_resched() not be a no-op; making cond_resched()
not be a no-op, but only when running tracing benchmarks; reverting
the aforementioned commit (which works because cond_resched_rcu_qs()
does provide an RCU-tasks quiescent state; and adding a call to the
scheduler/RCU rcu_note_voluntary_context_switch() function. All were
deemed unsatisfactory, either due to added cond_resched() overhead or
due to magic functions inviting cargo culting.
This commit renames cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs(),
which provides a clear hint as to what this function is doing and
why and where it should be used, and then replaces the call to
cond_resched() with cond_resched_tasks_rcu_qs() in the trace benchmark's
benchmark_event_kthread() function.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
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If an excessive number of callbacks have been queued, but the NOCB
leader kthread's wakeup must be deferred, then we should wake up the
leader unconditionally once it is safe to do so.
This was handled correctly in commit fbce7497ee ("rcu: Parallelize and
economize NOCB kthread wakeups"), but then commit 8be6e1b15c ("rcu:
Use timer as backstop for NOCB deferred wakeups") passed RCU_NOCB_WAKE
instead of the correct RCU_NOCB_WAKE_FORCE to wake_nocb_leader_defer().
As an interesting aside, RCU_NOCB_WAKE_FORCE is never passed to anything,
which should have been taken as a hint. ;-)
This commit therefore passes RCU_NOCB_WAKE_FORCE instead of RCU_NOCB_WAKE
to wake_nocb_leader_defer() when a callback is queued onto a NOCB CPU
that already has an excessive number of callbacks pending.
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
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Commit 44c65ff2e3b0 ("rcu: Eliminate NOCBs CPU-state Kconfig options")
made allocation of rcu_nocb_mask depend only on the rcu_nocbs=,
nohz_full=, or isolcpus= kernel boot parameters. However, it failed
to change the initial value of rcu_init_nohz()'s local variable
need_rcu_nocb_mask to false, which can result in useless allocation
of an all-zero rcu_nocb_mask. This commit therefore fixes this bug by
changing the initial value of need_rcu_nocb_mask to false.
While we are in the area, also correct the error message that is printed
when someone specifies that can-never-exist CPUs should be NOCBs CPUs.
Reported-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Byungchul Park <byungchul.park@lge.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
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The rcu_preempt_do_callbacks() function was introduced in commit
09223371dea(rcu: Use softirq to address performance regression), where it
was necessary to handle kernel builds both containing and not containing
RCU-preempt. Since then, various changes (most notably f8b7fc6b51
("rcu: use softirq instead of kthreads except when RCU_BOOST=y")) have
resulted in this function being invoked only from rcu_kthread_do_work(),
which is present only in kernels containing RCU-preempt, which in turn
means that the rcu_preempt_do_callbacks() function is no longer needed.
This commit therefore inlines rcu_preempt_do_callbacks() into its
sole remaining caller and also removes the rcu_state_p and rcu_data_p
indirection for added clarity.
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
[ paulmck: Remove the rcu_state_p and rcu_data_p indirection. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
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Commits c0b334c5bfa9 and ea9b0c8a26a2 introduced new sparse warnings
by accessing rcu_node->lock directly and ignoring the __private
marker. Introduce a new wrapper and use it. Also fix a similar problem
in srcutree.c introduced by a3883df3935e.
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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The debugfs interface displayed statistics on RCU callback invocation but
this interface has since been removed. This commit therefore removes the
no-longer-used rcu_data structure's ->n_cbs_invoked and ->n_nocbs_invoked
fields along with their updates.
If this information proves necessary in the future, the corresponding
event traces will be added.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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The debugfs interface displayed statistics on RCU priority boosting,
but this interface has since been removed. This commit therefore
removes the no-longer-used rcu_data structure's ->n_tasks_boosted,
->n_exp_boosts, and ->n_exp_boosts and their updates.
If this information proves necessary in the future, the corresponding
event traces will be added.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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When RCU stall warning triggers, it can print out a lot of messages
while holding spinlocks. If the console device is slow (e.g. an
actual or IPMI serial console), it may end up triggering NMI hard
lockup watchdog like the following.
*** CPU printking while holding RCU spinlock
PID: 4149739 TASK: ffff881a46baa880 CPU: 13 COMMAND: "CPUThreadPool8"
#0 [ffff881fff945e48] crash_nmi_callback at ffffffff8103f7d0
#1 [ffff881fff945e58] nmi_handle at ffffffff81020653
#2 [ffff881fff945eb0] default_do_nmi at ffffffff81020c36
#3 [ffff881fff945ed0] do_nmi at ffffffff81020d32
#4 [ffff881fff945ef0] end_repeat_nmi at ffffffff81956a7e
[exception RIP: io_serial_in+21]
RIP: ffffffff81630e55 RSP: ffff881fff943b88 RFLAGS: 00000002
RAX: 000000000000ca00 RBX: ffffffff8230e188 RCX: 0000000000000000
RDX: 00000000000002fd RSI: 0000000000000005 RDI: ffffffff8230e188
RBP: ffff881fff943bb0 R8: 0000000000000000 R9: ffffffff820cb3c4
R10: 0000000000000019 R11: 0000000000002000 R12: 00000000000026e1
R13: 0000000000000020 R14: ffffffff820cd398 R15: 0000000000000035
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0000
--- <NMI exception stack> ---
#5 [ffff881fff943b88] io_serial_in at ffffffff81630e55
#6 [ffff881fff943b90] wait_for_xmitr at ffffffff8163175c
#7 [ffff881fff943bb8] serial8250_console_putchar at ffffffff816317dc
#8 [ffff881fff943bd8] uart_console_write at ffffffff8162ac00
#9 [ffff881fff943c08] serial8250_console_write at ffffffff81634691
#10 [ffff881fff943c80] univ8250_console_write at ffffffff8162f7c2
#11 [ffff881fff943c90] console_unlock at ffffffff810dfc55
#12 [ffff881fff943cf0] vprintk_emit at ffffffff810dffb5
#13 [ffff881fff943d50] vprintk_default at ffffffff810e01bf
#14 [ffff881fff943d60] vprintk_func at ffffffff810e1127
#15 [ffff881fff943d70] printk at ffffffff8119a8a4
#16 [ffff881fff943dd0] print_cpu_stall_info at ffffffff810eb78c
#17 [ffff881fff943e88] rcu_check_callbacks at ffffffff810ef133
#18 [ffff881fff943ee8] update_process_times at ffffffff810f3497
#19 [ffff881fff943f10] tick_sched_timer at ffffffff81103037
#20 [ffff881fff943f38] __hrtimer_run_queues at ffffffff810f3f38
#21 [ffff881fff943f88] hrtimer_interrupt at ffffffff810f442b
*** CPU triggering the hardlockup watchdog
PID: 4149709 TASK: ffff88010f88c380 CPU: 26 COMMAND: "CPUThreadPool35"
#0 [ffff883fff1059d0] machine_kexec at ffffffff8104a874
#1 [ffff883fff105a30] __crash_kexec at ffffffff811116cc
#2 [ffff883fff105af0] __crash_kexec at ffffffff81111795
#3 [ffff883fff105b08] panic at ffffffff8119a6ae
#4 [ffff883fff105b98] watchdog_overflow_callback at ffffffff81135dbd
#5 [ffff883fff105bb0] __perf_event_overflow at ffffffff81186866
#6 [ffff883fff105be8] perf_event_overflow at ffffffff81192bc4
#7 [ffff883fff105bf8] intel_pmu_handle_irq at ffffffff8100b265
#8 [ffff883fff105df8] perf_event_nmi_handler at ffffffff8100489f
#9 [ffff883fff105e58] nmi_handle at ffffffff81020653
#10 [ffff883fff105eb0] default_do_nmi at ffffffff81020b94
#11 [ffff883fff105ed0] do_nmi at ffffffff81020d32
#12 [ffff883fff105ef0] end_repeat_nmi at ffffffff81956a7e
[exception RIP: queued_spin_lock_slowpath+248]
RIP: ffffffff810da958 RSP: ffff883fff103e68 RFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000046 RCX: 00000000006d0000
RDX: ffff883fff49a950 RSI: 0000000000d10101 RDI: ffffffff81e54300
RBP: ffff883fff103e80 R8: ffff883fff11a950 R9: 0000000000000000
R10: 000000000e5873ba R11: 000000000000010f R12: ffffffff81e54300
R13: 0000000000000000 R14: ffff88010f88c380 R15: ffffffff81e54300
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
--- <NMI exception stack> ---
#13 [ffff883fff103e68] queued_spin_lock_slowpath at ffffffff810da958
#14 [ffff883fff103e70] _raw_spin_lock_irqsave at ffffffff8195550b
#15 [ffff883fff103e88] rcu_check_callbacks at ffffffff810eed18
#16 [ffff883fff103ee8] update_process_times at ffffffff810f3497
#17 [ffff883fff103f10] tick_sched_timer at ffffffff81103037
#18 [ffff883fff103f38] __hrtimer_run_queues at ffffffff810f3f38
#19 [ffff883fff103f88] hrtimer_interrupt at ffffffff810f442b
--- <IRQ stack> ---
Avoid spuriously triggering NMI hardlockup watchdog by touching it
from the print functions. show_state_filter() shares the same problem
and solution.
v2: Relocate the comment to where it belongs.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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In CONFIG_RCU_NOCB_CPU=y kernels, if the boot parameters indicate that
none of the CPUs should in fact be offloaded, the following somewhat
obtuse message appears:
Offload RCU callbacks from CPUs: .
This commit therefore makes the message at least grammatically correct
in this case:
Offload RCU callbacks from CPUs: (none)
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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'fixes.2017.12.11a', 'srbd.2017.12.05a' and 'torture.2017.12.11a' into HEAD
cond_resched.2017.12.04a: Convert cond_resched_rcu_qs() to cond_resched()
dyntick.2017.11.28a: Make RCU dynticks handle interrupts from NMI
fixes.2017.12.11a: Miscellaneous fixes
srbd.2017.12.05a: Remove now-redundant smp_read_barrier_depends()
torture.2017.12.11a: Torture-testing update
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Currently have_rcu_nocb_mask is used to avoid double allocation of
rcu_nocb_mask during boot up. Due to different representation of
cpumask_var_t on different kernel config CPUMASK=y(or n) it was okay.
But now we have a helper cpumask_available(), which can be utilized
to check whether rcu_nocb_mask has been allocated or not without using
a variable.
Removing the variable also reduces vmlinux size.
Unpatched version:
text data bss dec hex filename
13050393 7852470 14543408 35446271 21cddff vmlinux
Patched version:
text data bss dec hex filename
13050390 7852438 14543408 35446236 21cdddc vmlinux
Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Because the ->dynticks_nesting field now only contains the process-based
nesting level instead of a value encoding both the process nesting level
and the irq "nesting" level, we no longer need a long long, even on
32-bit systems. This commit therefore changes both the ->dynticks_nesting
and ->dynticks_nmi_nesting fields to long.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"Yet another big pile of changes:
- More year 2038 work from Arnd slowly reaching the point where we
need to think about the syscalls themself.
- A new timer function which allows to conditionally (re)arm a timer
only when it's either not running or the new expiry time is sooner
than the armed expiry time. This allows to use a single timer for
multiple timeout requirements w/o caring about the first expiry
time at the call site.
- A new NMI safe accessor to clock real time for the printk timestamp
work. Can be used by tracing, perf as well if required.
- A large number of timer setup conversions from Kees which got
collected here because either maintainers requested so or they
simply got ignored. As Kees pointed out already there are a few
trivial merge conflicts and some redundant commits which was
unavoidable due to the size of this conversion effort.
- Avoid a redundant iteration in the timer wheel softirq processing.
- Provide a mechanism to treat RTC implementations depending on their
hardware properties, i.e. don't inflict the write at the 0.5
seconds boundary which originates from the PC CMOS RTC to all RTCs.
No functional change as drivers need to be updated separately.
- The usual small updates to core code clocksource drivers. Nothing
really exciting"
* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (111 commits)
timers: Add a function to start/reduce a timer
pstore: Use ktime_get_real_fast_ns() instead of __getnstimeofday()
timer: Prepare to change all DEFINE_TIMER() callbacks
netfilter: ipvs: Convert timers to use timer_setup()
scsi: qla2xxx: Convert timers to use timer_setup()
block/aoe: discover_timer: Convert timers to use timer_setup()
ide: Convert timers to use timer_setup()
drbd: Convert timers to use timer_setup()
mailbox: Convert timers to use timer_setup()
crypto: Convert timers to use timer_setup()
drivers/pcmcia: omap1: Fix error in automated timer conversion
ARM: footbridge: Fix typo in timer conversion
drivers/sgi-xp: Convert timers to use timer_setup()
drivers/pcmcia: Convert timers to use timer_setup()
drivers/memstick: Convert timers to use timer_setup()
drivers/macintosh: Convert timers to use timer_setup()
hwrng/xgene-rng: Convert timers to use timer_setup()
auxdisplay: Convert timers to use timer_setup()
sparc/led: Convert timers to use timer_setup()
mips: ip22/32: Convert timers to use timer_setup()
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
"The main updates in this cycle were:
- Group balancing enhancements and cleanups (Brendan Jackman)
- Move CPU isolation related functionality into its separate
kernel/sched/isolation.c file, with related 'housekeeping_*()'
namespace and nomenclature et al. (Frederic Weisbecker)
- Improve the interactive/cpu-intense fairness calculation (Josef
Bacik)
- Improve the PELT code and related cleanups (Peter Zijlstra)
- Improve the logic of pick_next_task_fair() (Uladzislau Rezki)
- Improve the RT IPI based balancing logic (Steven Rostedt)
- Various micro-optimizations:
- better !CONFIG_SCHED_DEBUG optimizations (Patrick Bellasi)
- better idle loop (Cheng Jian)
- ... plus misc fixes, cleanups and updates"
* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
sched/core: Optimize sched_feat() for !CONFIG_SCHED_DEBUG builds
sched/sysctl: Fix attributes of some extern declarations
sched/isolation: Document isolcpus= boot parameter flags, mark it deprecated
sched/isolation: Add basic isolcpus flags
sched/isolation: Move isolcpus= handling to the housekeeping code
sched/isolation: Handle the nohz_full= parameter
sched/isolation: Introduce housekeeping flags
sched/isolation: Split out new CONFIG_CPU_ISOLATION=y config from CONFIG_NO_HZ_FULL
sched/isolation: Rename is_housekeeping_cpu() to housekeeping_cpu()
sched/isolation: Use its own static key
sched/isolation: Make the housekeeping cpumask private
sched/isolation: Provide a dynamic off-case to housekeeping_any_cpu()
sched/isolation, watchdog: Use housekeeping_cpumask() instead of ad-hoc version
sched/isolation: Move housekeeping related code to its own file
sched/idle: Micro-optimize the idle loop
sched/isolcpus: Fix "isolcpus=" boot parameter handling when !CONFIG_CPUMASK_OFFSTACK
x86/tsc: Append the 'tsc=' description for the 'tsc=unstable' boot parameter
sched/rt: Simplify the IPI based RT balancing logic
block/ioprio: Use a helper to check for RT prio
sched/rt: Add a helper to test for a RT task
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull core locking updates from Ingo Molnar:
"The main changes in this cycle are:
- Another attempt at enabling cross-release lockdep dependency
tracking (automatically part of CONFIG_PROVE_LOCKING=y), this time
with better performance and fewer false positives. (Byungchul Park)
- Introduce lockdep_assert_irqs_enabled()/disabled() and convert
open-coded equivalents to lockdep variants. (Frederic Weisbecker)
- Add down_read_killable() and use it in the VFS's iterate_dir()
method. (Kirill Tkhai)
- Convert remaining uses of ACCESS_ONCE() to
READ_ONCE()/WRITE_ONCE(). Most of the conversion was Coccinelle
driven. (Mark Rutland, Paul E. McKenney)
- Get rid of lockless_dereference(), by strengthening Alpha atomics,
strengthening READ_ONCE() with smp_read_barrier_depends() and thus
being able to convert users of lockless_dereference() to
READ_ONCE(). (Will Deacon)
- Various micro-optimizations:
- better PV qspinlocks (Waiman Long),
- better x86 barriers (Michael S. Tsirkin)
- better x86 refcounts (Kees Cook)
- ... plus other fixes and enhancements. (Borislav Petkov, Juergen
Gross, Miguel Bernal Marin)"
* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
locking/x86: Use LOCK ADD for smp_mb() instead of MFENCE
rcu: Use lockdep to assert IRQs are disabled/enabled
netpoll: Use lockdep to assert IRQs are disabled/enabled
timers/posix-cpu-timers: Use lockdep to assert IRQs are disabled/enabled
sched/clock, sched/cputime: Use lockdep to assert IRQs are disabled/enabled
irq_work: Use lockdep to assert IRQs are disabled/enabled
irq/timings: Use lockdep to assert IRQs are disabled/enabled
perf/core: Use lockdep to assert IRQs are disabled/enabled
x86: Use lockdep to assert IRQs are disabled/enabled
smp/core: Use lockdep to assert IRQs are disabled/enabled
timers/hrtimer: Use lockdep to assert IRQs are disabled/enabled
timers/nohz: Use lockdep to assert IRQs are disabled/enabled
workqueue: Use lockdep to assert IRQs are disabled/enabled
irq/softirqs: Use lockdep to assert IRQs are disabled/enabled
locking/lockdep: Add IRQs disabled/enabled assertion APIs: lockdep_assert_irqs_enabled()/disabled()
locking/pvqspinlock: Implement hybrid PV queued/unfair locks
locking/rwlocks: Fix comments
x86/paravirt: Set up the virt_spin_lock_key after static keys get initialized
block, locking/lockdep: Assign a lock_class per gendisk used for wait_for_completion()
workqueue: Remove now redundant lock acquisitions wrt. workqueue flushes
...
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Lockdep now has an integrated IRQs disabled/enabled sanity check. Just
use it instead of the ad-hoc RCU version.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David S . Miller <davem@davemloft.net>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/1509980490-4285-15-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Paul E. McKenney
Joe Perches
Boqun Feng
Peter Zijlstra
Byungchul Park
Matthew Wilcox
Tejun Heo
Rakib Mullick
Linus Torvalds
Frederic Weisbecker