The patch titled
srcu-3: improved comment and code-style improvements from Joe Perches
has been added to the -mm tree. Its filename is
srcu-3-rcu-variant-permitting-read-side-blocking-fix.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: srcu-3: improved comment and code-style improvements from Joe Perches
From: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
An improved comment for synchronize_srcu() and fixes for code-style bugs
pointed out by off-list by Joe Perches.
Cc: Joe Perches <joe@xxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
kernel/srcu.c | 14 +++++++-------
1 files changed, 7 insertions(+), 7 deletions(-)
diff -puN kernel/srcu.c~srcu-3-rcu-variant-permitting-read-side-blocking-fix kernel/srcu.c
--- a/kernel/srcu.c~srcu-3-rcu-variant-permitting-read-side-blocking-fix
+++ a/kernel/srcu.c
@@ -62,7 +62,7 @@ static int srcu_readers_active_idx(struc
sum = 0;
for_each_possible_cpu(cpu)
sum += per_cpu_ptr(sp->per_cpu_ref, cpu)->c[idx];
- return (sum);
+ return sum;
}
/**
@@ -144,11 +144,15 @@ void srcu_read_unlock(struct srcu_struct
* As with classic RCU, the updater must use some separate means of
* synchronizing concurrent updates. Can block; must be called from
* process context.
+ *
+ * Note that it is illegal to call synchornize_srcu() from the corresponding
+ * SRCU read-side critical section; doing so will result in deadlock.
+ * However, it is perfectly legal to call synchronize_srcu() on one
+ * srcu_struct from some other srcu_struct's read-side critical section.
*/
void synchronize_srcu(struct srcu_struct *sp)
{
int idx;
- int sum;
idx = sp->completed;
mutex_lock(&sp->mutex);
@@ -195,12 +199,8 @@ void synchronize_srcu(struct srcu_struct
* will have finished executing.
*/
- for (;;) {
- sum = srcu_readers_active_idx(sp, idx);
- if (sum == 0)
- break;
+ while (srcu_readers_active_idx(sp, idx))
schedule_timeout_interruptible(1);
- }
synchronize_sched(); /* Force memory barrier on all CPUs. */
_
Patches currently in -mm which might be from paulmck@xxxxxxxxxx are
rcu-documentation-fix.patch
radix-tree-rcu-lockless-readside.patch
adix-tree-rcu-lockless-readside-update.patch
srcu-3-rcu-variant-permitting-read-side-blocking.patch
srcu-3-rcu-variant-permitting-read-side-blocking-fix.patch
srcu-3-add-srcu-operations-to-rcutorture.patch
-
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