On 2021/2/23 7:50 下午, Xie Yongji wrote:
Increase the recursion depth of eventfd_signal() to 1. This
is the maximum recursion depth we have found so far.
Signed-off-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
It might be useful to explain how/when we can reach for this condition.
Thanks
---
fs/eventfd.c | 2 +-
include/linux/eventfd.h | 5 ++++-
2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/eventfd.c b/fs/eventfd.c
index e265b6dd4f34..cc7cd1dbedd3 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -71,7 +71,7 @@ __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
* it returns true, the eventfd_signal() call should be deferred to a
* safe context.
*/
- if (WARN_ON_ONCE(this_cpu_read(eventfd_wake_count)))
+ if (WARN_ON_ONCE(this_cpu_read(eventfd_wake_count) > EFD_WAKE_DEPTH))
return 0;
spin_lock_irqsave(&ctx->wqh.lock, flags);
diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h
index fa0a524baed0..886d99cd38ef 100644
--- a/include/linux/eventfd.h
+++ b/include/linux/eventfd.h
@@ -29,6 +29,9 @@
#define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
#define EFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS | EFD_SEMAPHORE)
+/* Maximum recursion depth */
+#define EFD_WAKE_DEPTH 1
+
struct eventfd_ctx;
struct file;
@@ -47,7 +50,7 @@ DECLARE_PER_CPU(int, eventfd_wake_count);
static inline bool eventfd_signal_count(void)
{
- return this_cpu_read(eventfd_wake_count);
+ return this_cpu_read(eventfd_wake_count) > EFD_WAKE_DEPTH;
}
#else /* CONFIG_EVENTFD */
_______________________________________________
Virtualization mailing list
Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
