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  1. 14 6月, 2019 1 次提交
  3. 29 5月, 2019 1 次提交
  5. 27 3月, 2019 1 次提交
    • N
      rcu: Do a single rhp->func read in rcu_head_after_call_rcu() · b699cce1
      由 Neeraj Upadhyay 提交于 
      The rcu_head_after_call_rcu() function reads the rhp->func pointer twice,
which can result in a false-positive WARN_ON_ONCE() if the callback
were passed to call_rcu() between the two reads.  Although racing
rcu_head_after_call_rcu() with call_rcu() is to be a dubious use case
(the return value is not reliable in that case), intermittent and
irreproducible warnings are also quite dubious.  This commit therefore
uses a single READ_ONCE() to pick up the value of rhp->func once, then
tests that value twice, thus guaranteeing consistent processing within
rcu_head_after_call_rcu()().

Neverthless, racing rcu_head_after_call_rcu() with call_rcu() is still
a dubious use case.
Signed-off-by: NNeeraj Upadhyay <neeraju@codeaurora.org>
[ paulmck: Add blank line after declaration per checkpatch.pl. ]
Signed-off-by: NPaul E. McKenney <paulmck@linux.ibm.com>
      b699cce1
  7. 10 2月, 2019 1 次提交
  9. 26 1月, 2019 4 次提交
    • J
      rcu: Add sparse check to rcu_assign_pointer() · 423a86a6
      由 Joel Fernandes (Google) 提交于 
      The rcu_assign_pointer() function currently doesn't do any sparse checking
on the assigned-to pointer.  So its possible that a pointer that is
not __rcu annotated is assigned with rcu_assign_pointer without sparse
complaints.  Because rcu_dereference() already does such checking,
this commit makes rcu_assign_pointer() to do the same. The extra
error could be helpful in cases where an RCU pointer is assigned with
rcu_assign_pointer() but not annotated with __rcu.

This doesn't generate any code in the normal case because __CHECKER__ is
defined only in the context of sparse.

This commit also renames rcu_dereference_sparse() to rcu_check_parse()
since the checking now happens not only during derereferencing but also
during assignment.

Test: Introduced an rcu_assign_pointer in code and checked the output of
sparse with and without this change. The change correctly causes sparse
to throw an error.
Signed-off-by: NJoel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: NPaul E. McKenney <paulmck@linux.ibm.com>
      423a86a6
    • P
      rcu: Rename rcu_check_callbacks() to rcu_sched_clock_irq() · c98cac60
      由 Paul E. McKenney 提交于 
      The name rcu_check_callbacks() arguably made sense back in the early
2000s when RCU was quite a bit simpler than it is today, but it has
become quite misleading, especially with the advent of dyntick-idle
and NO_HZ_FULL.  The rcu_check_callbacks() function is RCU's hook into
the scheduling-clock interrupt, and is now but one of many ways that
callbacks get promoted to invocable state.

This commit therefore changes the name to rcu_sched_clock_irq(),
which is the same number of characters and clearly indicates this
function's relation to the rest of the Linux kernel.  In addition, for
the sake of consistency, rcu_flavor_check_callbacks() is also renamed
to rcu_flavor_sched_clock_irq().

While in the area, the header comments for both functions are reworked.
Signed-off-by: NPaul E. McKenney <paulmck@linux.ibm.com>
      c98cac60
    • P
      rcu: Docbook for rcu_head_init() and rcu_head_after_call_rcu() · 2aa55030
      由 Paul E. McKenney 提交于 
      This commit adds the missing asterisks required to make Sphinx pick up
the current header comments for these two functions.
Signed-off-by: NPaul E. McKenney <paulmck@linux.ibm.com>
      2aa55030
    • P
      rcu: Remove wrapper definitions for obsolete RCU update functions · 6ba7d681
      由 Paul E. McKenney 提交于 
      None of synchronize_rcu_bh, synchronize_rcu_bh_expedited, call_rcu_bh,
rcu_barrier_bh, synchronize_sched, synchronize_sched_expedited,
call_rcu_sched, rcu_barrier_sched, get_state_synchronize_sched, and
cond_synchronize_sched are actually used.  This commit therefore removes
their trivial wrapper-function definitions.
Signed-off-by: NPaul E. McKenney <paulmck@linux.ibm.com>
      6ba7d681
  11. 31 8月, 2018 9 次提交
  13. 13 7月, 2018 4 次提交
  15. 10 6月, 2018 1 次提交
  17. 23 5月, 2018 1 次提交
  19. 16 5月, 2018 1 次提交
    • P
      rcu: Rename cond_resched_rcu_qs() to cond_resched_tasks_rcu_qs() · cee43939
      由 Paul E. McKenney 提交于 
      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
  21. 21 2月, 2018 1 次提交
  23. 17 12月, 2017 1 次提交
  25. 05 12月, 2017 2 次提交
  27. 24 10月, 2017 1 次提交
  29. 20 10月, 2017 1 次提交
  31. 30 8月, 2017 1 次提交
  33. 17 8月, 2017 2 次提交
  35. 26 7月, 2017 1 次提交
    • P
      rcu: Migrate callbacks earlier in the CPU-offline timeline · a58163d8
      由 Paul E. McKenney 提交于 
      RCU callbacks must be migrated away from an outgoing CPU, and this is
done near the end of the CPU-hotplug operation, after the outgoing CPU is
long gone.  Unfortunately, this means that other CPU-hotplug callbacks
can execute while the outgoing CPU's callbacks are still immobilized
on the long-gone CPU's callback lists.  If any of these CPU-hotplug
callbacks must wait, either directly or indirectly, for the invocation
of any of the immobilized RCU callbacks, the system will hang.

This commit avoids such hangs by migrating the callbacks away from the
outgoing CPU immediately upon its departure, shortly after the return
from __cpu_die() in takedown_cpu().  Thus, RCU is able to advance these
callbacks and invoke them, which allows all the after-the-fact CPU-hotplug
callbacks to wait on these RCU callbacks without risk of a hang.

While in the neighborhood, this commit also moves rcu_send_cbs_to_orphanage()
and rcu_adopt_orphan_cbs() under a pre-existing #ifdef to avoid including
dead code on the one hand and to avoid define-without-use warnings on the
other hand.
Reported-by: NJeffrey Hugo <jhugo@codeaurora.org>
Link: http://lkml.kernel.org/r/db9c91f6-1b17-6136-84f0-03c3c2581ab4@codeaurora.orgSigned-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Richard Weinberger <richard@nod.at>
      a58163d8
  37. 25 7月, 2017 1 次提交
  39. 09 6月, 2017 5 次提交