提交 · c3442697c2d73d3cdb9d4135cf630ad36ba8552f · openanolis / cloud-kernel

16 5月, 2018 6 次提交

softirq: Eliminate unused cond_resched_softirq() macro · c3442697

由 Paul E. McKenney 提交于 3月 05, 2018

The cond_resched_softirq() macro is not used anywhere in mainline, so
this commit simplifies the kernel by eliminating it.
Suggested-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: NEric Dumazet <edumazet@google.com>
Tested-by: NNicholas Piggin <npiggin@gmail.com>

c3442697

rcu: Rename cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs() · cee43939

由 Paul E. McKenney 提交于 3月 02, 2018

Commit e31d28b6 ("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: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: NNicholas Piggin <npiggin@gmail.com>

cee43939

rcu: Remove deprecated RCU debugfs tracing code · 6fba2b37

由 Byungchul Park 提交于 3月 02, 2018

Commit ae91aa0a ("rcu: Remove debugfs tracing") removed the
RCU debugfs tracing code, but did not remove the no-longer used
->exp_workdone{0,1,2,3} fields in the srcu_data structure.  This commit
therefore removes these fields along with the code that uselessly
updates them.
Signed-off-by: NByungchul Park <byungchul.park@lge.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: NNicholas Piggin <npiggin@gmail.com>

6fba2b37

rcu: Call wake_nocb_leader_defer() with 'FORCE' when nocb_q_count is high · efcd2d54

由 Byungchul Park 提交于 2月 28, 2018

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 fbce7497 ("rcu: Parallelize and
economize NOCB kthread wakeups"), but then commit 8be6e1b1 ("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: NByungchul Park <byungchul.park@lge.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: NNicholas Piggin <npiggin@gmail.com>

efcd2d54

rcu: Don't allocate rcu_nocb_mask if no one needs it · ef126206

由 Paul E. McKenney 提交于 2月 28, 2018

Commit 44c65ff2 ("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: NByungchul Park <byungchul.park@lge.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: NByungchul Park <byungchul.park@lge.com>
Tested-by: NNicholas Piggin <npiggin@gmail.com>

ef126206

rcu: Inline rcu_preempt_do_callback() into its sole caller · be01b4ca

由 Byungchul Park 提交于 2月 26, 2018

The rcu_preempt_do_callbacks() function was introduced in commit
09223371(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 f8b7fc6b
("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: NByungchul Park <byungchul.park@lge.com>
Reviewed-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
[ paulmck: Remove the rcu_state_p and rcu_data_p indirection. ]
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: NNicholas Piggin <npiggin@gmail.com>

be01b4ca

14 4月, 2018 14 次提交

kernel/kexec_file.c: allow archs to set purgatory load address · 3be3f61d