diff options
| author | Barret Rhoden | 2020-04-14 18:29:20 -0400 |
|---|---|---|
| committer | Peter Zijlstra | 2020-04-30 20:14:36 +0200 |
| commit | 2ed6edd33a214bca02bd2b45e3fc3038a059436b (patch) | |
| tree | fecc8c994d7afd07581c2a56ab07c617e9304150 /kernel/events | |
| parent | 3a4ac121c2cacbf97d493fa3bc42ead88657abe4 (diff) | |
perf: Add cond_resched() to task_function_call()
Under rare circumstances, task_function_call() can repeatedly fail and
cause a soft lockup.
There is a slight race where the process is no longer running on the cpu
we targeted by the time remote_function() runs. The code will simply
try again. If we are very unlucky, this will continue to fail, until a
watchdog fires. This can happen in a heavily loaded, multi-core virtual
machine.
Reported-by: syzbot+bb4935a5c09b5ff79940@syzkaller.appspotmail.com
Signed-off-by: Barret Rhoden <brho@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200414222920.121401-1-brho@google.com
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/core.c | 23 |
1 files changed, 14 insertions, 9 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 52951e9e8e1b..80cf996a7f19 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -95,11 +95,11 @@ static void remote_function(void *data) * @info: the function call argument * * Calls the function @func when the task is currently running. This might - * be on the current CPU, which just calls the function directly + * be on the current CPU, which just calls the function directly. This will + * retry due to any failures in smp_call_function_single(), such as if the + * task_cpu() goes offline concurrently. * - * returns: @func return value, or - * -ESRCH - when the process isn't running - * -EAGAIN - when the process moved away + * returns @func return value or -ESRCH when the process isn't running */ static int task_function_call(struct task_struct *p, remote_function_f func, void *info) @@ -112,11 +112,16 @@ task_function_call(struct task_struct *p, remote_function_f func, void *info) }; int ret; - do { - ret = smp_call_function_single(task_cpu(p), remote_function, &data, 1); - if (!ret) - ret = data.ret; - } while (ret == -EAGAIN); + for (;;) { + ret = smp_call_function_single(task_cpu(p), remote_function, + &data, 1); + ret = !ret ? data.ret : -EAGAIN; + + if (ret != -EAGAIN) + break; + + cond_resched(); + } return ret; } |