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| author | Li Zhong <zhong@linux.vnet.ibm.com> | 2012-07-24 15:02:49 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-10-02 10:30:35 -0700 |
| commit | 11266a8e031a3782241760850f002c79ee2887e1 (patch) | |
| tree | 4adf182d24be78556d51eb6e96fbb6c89c99707a /kernel/async.c | |
| parent | 0d19c30f548369606cce202224c86cf3ae1d20ea (diff) | |
Fix a dead loop in async_synchronize_full()
[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 <paulmck@linux.vnet.ibm.com>
Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Christian Kujau <lists@nerdbynature.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Williams <dan.j.williams@gmail.com>
Cc: Christian Kujau <lists@nerdbynature.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/async.c')
| -rw-r--r-- | kernel/async.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/kernel/async.c b/kernel/async.c index bd0c168a3bb..32d8dc96026 100644 --- a/kernel/async.c +++ b/kernel/async.c @@ -86,6 +86,13 @@ static async_cookie_t __lowest_in_progress(struct list_head *running) { 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_domain); /** * 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 |