diff options
| author | Jens Axboe <axboe@kernel.dk> | 2020-02-02 08:23:03 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2020-02-03 17:27:38 -0700 |
| commit | b5e683d5cab8cd433b06ae178621f083cabd4f63 (patch) | |
| tree | ff80c1fcdd40441ae015b35d67897c1f63129a9c /include/linux | |
| parent | d7f62e825fd19202a0749d10fb439714c51f67d2 (diff) | |
eventfd: track eventfd_signal() recursion depth
eventfd use cases from aio and io_uring can deadlock due to circular
or resursive calling, when eventfd_signal() tries to grab the waitqueue
lock. On top of that, it's also possible to construct notification
chains that are deep enough that we could blow the stack.
Add a percpu counter that tracks the percpu recursion depth, warn if we
exceed it. The counter is also exposed so that users of eventfd_signal()
can do the right thing if it's non-zero in the context where it is
called.
Cc: stable@vger.kernel.org # 4.19+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/eventfd.h | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h index ffcc7724ca21..dc4fd8a6644d 100644 --- a/include/linux/eventfd.h +++ b/include/linux/eventfd.h @@ -12,6 +12,8 @@ #include <linux/fcntl.h> #include <linux/wait.h> #include <linux/err.h> +#include <linux/percpu-defs.h> +#include <linux/percpu.h> /* * CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining @@ -40,6 +42,13 @@ __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n); int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait, __u64 *cnt); +DECLARE_PER_CPU(int, eventfd_wake_count); + +static inline bool eventfd_signal_count(void) +{ + return this_cpu_read(eventfd_wake_count); +} + #else /* CONFIG_EVENTFD */ /* @@ -68,6 +77,11 @@ static inline int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, return -ENOSYS; } +static inline bool eventfd_signal_count(void) +{ + return false; +} + #endif #endif /* _LINUX_EVENTFD_H */ |