Accessing nohz_cpu_mask before incrementing rcp->cur is racy. It can cause
tickless idle CPUs to be included in rsp->cpumask, which will extend
graceperiods unnecessarily.
Fix this race. It has been tested using extensions to RCU torture module
that forces various CPUs to become idle.
Signed-off-by: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This introduces a new interface - rcu_barrier() which waits until all
the RCUs queued until this call have been completed.
Reiser4 needs this, because we do more than just freeing memory object
in our RCU callback: we also remove it from the list hanging off
super-block. This means, that before freeing reiser4-specific portion
of super-block (during umount) we have to wait until all pending RCU
callbacks are executed.
The only change of reiser4 made to the original patch, is exporting of
rcu_barrier().
Cc: Hans Reiser <reiser@namesys.com>
Cc: Vladimir V. Saveliev <vs@namesys.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch is a rewrite of the one submitted on October 1st, using modules
(http://marc.theaimsgroup.com/?l=linux-kernel&m=112819093522998&w=2).
This rewrite adds a tristate CONFIG_RCU_TORTURE_TEST, which enables an
intense torture test of the RCU infratructure. This is needed due to the
continued changes to the RCU infrastructure to accommodate dynamic ticks,
CPU hotplug, realtime, and so on. Most of the code is in a separate file
that is compiled only if the CONFIG variable is set. Documentation on how
to run the test and interpret the output is also included.
This code has been tested on i386 and ppc64, and an earlier version of the
code has received extensive testing on a number of architectures as part of
the PREEMPT_RT patchset.
Signed-off-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This makes call_rcu() keep track of how many events there are on the RCU
list, and cause a reschedule event when the list gets too long.
This helps keep RCU event lists down.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Dipankar made RCU limit the batch size to improve latency, but that
approach is unworkable: it can cause the RCU queues to grow without
bounds, since the batch limiter ended up limiting the callbacks.
So make the limit much higher, and start planning on instead limiting
the batch size by doing RCU callbacks more often if the queue looks like
it might be growing too long.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Adds a set of primitives to do reference counting for objects that are looked
up without locks using RCU.
Signed-off-by: Ravikiran Thirumalai <kiran_th@gmail.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The synchronize_kernel() primitive is used for quite a few different purposes:
waiting for RCU readers, waiting for NMIs, waiting for interrupts, and so on.
This makes RCU code harder to read, since synchronize_kernel() might or might
not have matching rcu_read_lock()s. This patch creates a new
synchronize_rcu() that is to be used for RCU readers and a new
synchronize_sched() that is used for the rest. These two new primitives
currently have the same implementation, but this is might well change with
additional real-time support. Both new primitives are GPL-only, the old
primitive is deprecated.
Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The gpl exports need to be put back. Moving them to GPL -- but in a
measured manner, as I proposed on this list some months ago -- is fine.
Changing these particular exports precipitously is most definitely -not-
fine. Here is my earlier proposal:
http://marc.theaimsgroup.com/?l=linux-kernel&m=110520930301813&w=2
See below for a patch that puts the exports back, along with an updated
version of my earlier patch that starts the process of moving them to GPL.
I will also be following this message with RFC patches that introduce two
(EXPORT_SYMBOL_GPL) interfaces to replace synchronize_kernel(), which then
becomes deprecated.
Signed-off-by: <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Srivatsa Vaddagiri