diff options
| author | Dipankar Sarma | 2005-12-12 00:37:05 -0800 |
|---|---|---|
| committer | Linus Torvalds | 2005-12-12 08:57:42 -0800 |
| commit | ab4720ec76b756e1f8705e207a7b392b0453afd6 (patch) | |
| tree | 1c4235ec8ac0e8e7f75a6f97ea6169e93647004f | |
| parent | 85b872424984e79519be904e7df02a91ba0a9486 (diff) | |
[PATCH] add rcu_barrier() synchronization point
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>
| -rw-r--r-- | include/linux/rcupdate.h | 2 | ||||
| -rw-r--r-- | kernel/rcupdate.c | 41 |
2 files changed, 43 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index cce25591eec2..a471f3bb713e 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -100,6 +100,7 @@ struct rcu_data { struct rcu_head *donelist; struct rcu_head **donetail; int cpu; + struct rcu_head barrier; }; DECLARE_PER_CPU(struct rcu_data, rcu_data); @@ -285,6 +286,7 @@ extern void FASTCALL(call_rcu_bh(struct rcu_head *head, extern __deprecated_for_modules void synchronize_kernel(void); extern void synchronize_rcu(void); void synchronize_idle(void); +extern void rcu_barrier(void); #endif /* __KERNEL__ */ #endif /* __LINUX_RCUPDATE_H */ diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index c4d159a21e04..f45b91723dc6 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -116,6 +116,10 @@ void fastcall call_rcu(struct rcu_head *head, local_irq_restore(flags); } +static atomic_t rcu_barrier_cpu_count; +static struct semaphore rcu_barrier_sema; +static struct completion rcu_barrier_completion; + /** * call_rcu_bh - Queue an RCU for invocation after a quicker grace period. * @head: structure to be used for queueing the RCU updates. @@ -162,6 +166,42 @@ long rcu_batches_completed(void) return rcu_ctrlblk.completed; } +static void rcu_barrier_callback(struct rcu_head *notused) +{ + if (atomic_dec_and_test(&rcu_barrier_cpu_count)) + complete(&rcu_barrier_completion); +} + +/* + * Called with preemption disabled, and from cross-cpu IRQ context. + */ +static void rcu_barrier_func(void *notused) +{ + int cpu = smp_processor_id(); + struct rcu_data *rdp = &per_cpu(rcu_data, cpu); + struct rcu_head *head; + + head = &rdp->barrier; + atomic_inc(&rcu_barrier_cpu_count); + call_rcu(head, rcu_barrier_callback); +} + +/** + * rcu_barrier - Wait until all the in-flight RCUs are complete. + */ +void rcu_barrier(void) +{ + BUG_ON(in_interrupt()); + /* Take cpucontrol semaphore to protect against CPU hotplug */ + down(&rcu_barrier_sema); + init_completion(&rcu_barrier_completion); + atomic_set(&rcu_barrier_cpu_count, 0); + on_each_cpu(rcu_barrier_func, NULL, 0, 1); + wait_for_completion(&rcu_barrier_completion); + up(&rcu_barrier_sema); +} +EXPORT_SYMBOL_GPL(rcu_barrier); + /* * Invoke the completed RCU callbacks. They are expected to be in * a per-cpu list. @@ -457,6 +497,7 @@ static struct notifier_block __devinitdata rcu_nb = { */ void __init rcu_init(void) { + sema_init(&rcu_barrier_sema, 1); rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long)smp_processor_id()); /* Register notifier for non-boot CPUs */ |