This is a note to let you know that I've just added the patch titled
Fix a dead loop in async_synchronize_full()
to the 3.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
fix-a-dead-loop-in-async_synchronize_full.patch
and it can be found in the queue-3.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From [email protected] Thu Sep 27 10:42:06 2012
From: Li Zhong <[email protected]>
Date: Tue, 24 Jul 2012 15:02:49 -0700
Subject: Fix a dead loop in async_synchronize_full()
From: Li Zhong <[email protected]>
[Fixed upstream by commits 2955b47d2c1983998a8c5915cb96884e67f7cb53 and
a4683487f90bfe3049686fc5c566bdc1ad03ace6 from Dan Williams, but they are much
more intrusive than this tiny fix, according to Andrew - gregkh]
This patch tries to fix a dead loop in async_synchronize_full(), which
could be seen when preemption is disabled on a single cpu machine.
void async_synchronize_full(void)
{
do {
async_synchronize_cookie(next_cookie);
} while (!list_empty(&async_running) || !
list_empty(&async_pending));
}
async_synchronize_cookie() calls async_synchronize_cookie_domain() with
&async_running as the default domain to synchronize.
However, there might be some works in the async_pending list from other
domains. On a single cpu system, without preemption, there is no chance
for the other works to finish, so async_synchronize_full() enters a dead
loop.
It seems async_synchronize_full() wants to synchronize all entries in
all running lists(domains), so maybe we could just check the entry_count
to know whether all works are finished.
Currently, async_synchronize_cookie_domain() expects a non-NULL running
list ( if NULL, there would be NULL pointer dereference ), so maybe a
NULL pointer could be used as an indication for the functions to
synchronize all works in all domains.
Reported-by: Paul E. McKenney <[email protected]>
Signed-off-by: Li Zhong <[email protected]>
Tested-by: Paul E. McKenney <[email protected]>
Tested-by: Christian Kujau <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Christian Kujau <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Cong Wang <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/async.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
--- a/kernel/async.c
+++ b/kernel/async.c
@@ -86,6 +86,13 @@ static async_cookie_t __lowest_in_progr
{
struct async_entry *entry;
+ if (!running) { /* just check the entry count */
+ if (atomic_read(&entry_count))
+ return 0; /* smaller than any cookie */
+ else
+ return next_cookie;
+ }
+
if (!list_empty(running)) {
entry = list_first_entry(running,
struct async_entry, list);
@@ -236,9 +243,7 @@ EXPORT_SYMBOL_GPL(async_schedule_domain)
*/
void async_synchronize_full(void)
{
- do {
- async_synchronize_cookie(next_cookie);
- } while (!list_empty(&async_running) || !list_empty(&async_pending));
+ async_synchronize_cookie_domain(next_cookie, NULL);
}
EXPORT_SYMBOL_GPL(async_synchronize_full);
@@ -258,7 +263,7 @@ EXPORT_SYMBOL_GPL(async_synchronize_full
/**
* async_synchronize_cookie_domain - synchronize asynchronous function calls
within a certain domain with cookie checkpointing
* @cookie: async_cookie_t to use as checkpoint
- * @running: running list to synchronize on
+ * @running: running list to synchronize on, NULL indicates all lists
*
* This function waits until all asynchronous function calls for the
* synchronization domain specified by the running list @list submitted
Patches currently in stable-queue which might be from [email protected]
are
queue-3.5/fix-a-dead-loop-in-async_synchronize_full.patch
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