diff options
author | Paul E. McKenney <paulmck@us.ibm.com> | 2006-10-04 02:17:02 -0700 |
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committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-10-04 07:55:30 -0700 |
commit | 621934ee7ed5b073c7fd638b347e632c53572761 (patch) | |
tree | 5722f9cda22c099ad60545f963410dcbc762ee65 /kernel/Makefile | |
parent | 95d77884c77beed676036d2f74d10b470a483c63 (diff) |
[PATCH] srcu-3: RCU variant permitting read-side blocking
Updated patch adding a variant of RCU that permits sleeping in read-side
critical sections. SRCU is as follows:
o Each use of SRCU creates its own srcu_struct, and each
srcu_struct has its own set of grace periods. This is
critical, as it prevents one subsystem with a blocking
reader from holding up SRCU grace periods for other
subsystems.
o The SRCU primitives (srcu_read_lock(), srcu_read_unlock(),
and synchronize_srcu()) all take a pointer to a srcu_struct.
o The SRCU primitives must be called from process context.
o srcu_read_lock() returns an int that must be passed to
the matching srcu_read_unlock(). Realtime RCU avoids the
need for this by storing the state in the task struct,
but SRCU needs to allow a given code path to pass through
multiple SRCU domains -- storing state in the task struct
would therefore require either arbitrary space in the
task struct or arbitrary limits on SRCU nesting. So I
kicked the state-storage problem up to the caller.
Of course, it is not permitted to call synchronize_srcu()
while in an SRCU read-side critical section.
o There is no call_srcu(). It would not be hard to implement
one, but it seems like too easy a way to OOM the system.
(Hey, we have enough trouble with call_rcu(), which does
-not- permit readers to sleep!!!) So, if you want it,
please tell me why...
[josht@us.ibm.com: sparse notation]
Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Josh Triplett <josh@freedesktop.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel/Makefile')
-rw-r--r-- | kernel/Makefile | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/Makefile b/kernel/Makefile index d948ca12acf0..5e3f3b75563a 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -8,7 +8,7 @@ obj-y = sched.o fork.o exec_domain.o panic.o printk.o profile.o \ signal.o sys.o kmod.o workqueue.o pid.o \ rcupdate.o extable.o params.o posix-timers.o \ kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \ - hrtimer.o rwsem.o latency.o nsproxy.o + hrtimer.o rwsem.o latency.o nsproxy.o srcu.o obj-$(CONFIG_STACKTRACE) += stacktrace.o obj-y += time/ |