| Message ID | 20210223115048.435-2-xieyongji@bytedance.com (mailing list archive) |
|---|---|
| State | RFC |
| Headers | show |
| Series | Introduce VDUSE - vDPA Device in Userspace | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
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@bytedance.com> Acked-by: Jason Wang <jasowang@redhat.com> 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 */
On Tue, Mar 2, 2021 at 2:44 PM Jason Wang <jasowang@redhat.com> wrote: > > > 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@bytedance.com> > > > Acked-by: Jason Wang <jasowang@redhat.com> > > It might be useful to explain how/when we can reach for this condition. > Fine. Thanks, Yongji
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 */
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@bytedance.com> --- fs/eventfd.c | 2 +- include/linux/eventfd.h | 5 ++++- 2 files changed, 5 insertions(+), 2 deletions(-)