user/sven/linux.git/include/linux/eventfd.h, branch v6.1.72

eventfd: provide a eventfd_signal_mask() helper

2023-01-04T10:28:48Z

[ Upstream commit 03e02acda8e267a8183e1e0ed289ff1ef9cd7ed8 ] This is identical to eventfd_signal(), but it allows the caller to pass in a mask to be used for the poll wakeup key. The use case is avoiding repeated multishot triggers if we have a dependency between eventfd and io_uring. If we setup an eventfd context and register that as the io_uring eventfd, and at the same time queue a multishot poll request for the eventfd context, then any CQE posted will repeatedly trigger the multishot request until it terminates when the CQ ring overflows. In preparation for io_uring detecting this circular dependency, add the mentioned helper so that io_uring can pass in EPOLL_URING as part of the poll wakeup key. Cc: stable@vger.kernel.org # 6.0 [axboe: fold in !CONFIG_EVENTFD fix from Zhang Qilong] Signed-off-by: Jens Axboe Stable-dep-of: 4464853277d0 ("io_uring: pass in EPOLL_URING_WAKE for eventfd signaling and wakeups") Signed-off-by: Sasha Levin

eventfd: change int to __u64 in eventfd_signal() ifndef CONFIG_EVENTFD

2022-12-31T12:32:00Z

[ Upstream commit fd4e60bf0ef8eb9edcfa12dda39e8b6ee9060492 ] Commit ee62c6b2dc93 ("eventfd: change int to __u64 in eventfd_signal()") forgot to change int to __u64 in the CONFIG_EVENTFD=n stub function. Link: https://lkml.kernel.org/r/20221124140154.104680-1-zhangqilong3@huawei.com Fixes: ee62c6b2dc93 ("eventfd: change int to __u64 in eventfd_signal()") Signed-off-by: Zhang Qilong Cc: Dylan Yudaken Cc: Jens Axboe Cc: Sha Zhengju Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin

eventfd: guard wake_up in eventfd fs calls as well

2022-09-21T16:30:42Z

Guard wakeups that the user can trigger, and that may end up triggering a call back into eventfd_signal. This is in addition to the current approach that only guards in eventfd_signal. Rename in_eventfd_signal -> in_eventfd at the same time to reflect this. Without this there would be a deadlock in the following code using libaio: int main() { struct io_context *ctx = NULL; struct iocb iocb; struct iocb *iocbs[] = { &iocb }; int evfd; uint64_t val = 1; evfd = eventfd(0, EFD_CLOEXEC); assert(!io_setup(2, &ctx)); io_prep_poll(&iocb, evfd, POLLIN); io_set_eventfd(&iocb, evfd); assert(1 == io_submit(ctx, 1, iocbs)); write(evfd, &val, 8); } Signed-off-by: Dylan Yudaken Reviewed-by: Jens Axboe Link: https://lore.kernel.org/r/20220816135959.1490641-1-dylany@fb.com Signed-off-by: Jens Axboe

eventfd: Make signal recursion protection a task bit

2021-08-27T23:33:02Z

The recursion protection for eventfd_signal() is based on a per CPU variable and relies on the !RT semantics of spin_lock_irqsave() for protecting this per CPU variable. On RT kernels spin_lock_irqsave() neither disables preemption nor interrupts which allows the spin lock held section to be preempted. If the preempting task invokes eventfd_signal() as well, then the recursion warning triggers. Paolo suggested to protect the per CPU variable with a local lock, but that's heavyweight and actually not necessary. The goal of this protection is to prevent the task stack from overflowing, which can be achieved with a per task recursion protection as well. Replace the per CPU variable with a per task bit similar to other recursion protection bits like task_struct::in_page_owner. This works on both !RT and RT kernels and removes as a side effect the extra per CPU storage. No functional change for !RT kernels. Reported-by: Daniel Bristot de Oliveira Signed-off-by: Thomas Gleixner Tested-by: Daniel Bristot de Oliveira Acked-by: Jason Wang Cc: Al Viro Link: https://lore.kernel.org/r/87wnp9idso.ffs@tglx

eventfd: Export eventfd_ctx_do_read()

2020-11-15T14:49:10Z

Where events are consumed in the kernel, for example by KVM's irqfd_wakeup() and VFIO's virqfd_wakeup(), they currently lack a mechanism to drain the eventfd's counter. Since the wait queue is already locked while the wakeup functions are invoked, all they really need to do is call eventfd_ctx_do_read(). Add a check for the lock, and export it for them. Signed-off-by: David Woodhouse Message-Id: <20201027135523.646811-2-dwmw2@infradead.org> Signed-off-by: Paolo Bonzini

eventfd: track eventfd_signal() recursion depth

2020-02-04T00:27:38Z

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

include/linux/eventfd.h: include linux/errno.h

2018-07-27T02:38:03Z

The new gasket staging driver ran into a randconfig build failure when CONFIG_EVENTFD is disabled: In file included from drivers/staging/gasket/gasket_interrupt.h:11, from drivers/staging/gasket/gasket_interrupt.c:4: include/linux/eventfd.h: In function 'eventfd_ctx_fdget': include/linux/eventfd.h:51:9: error: implicit declaration of function 'ERR_PTR' [-Werror=implicit-function-declaration] I can't see anything wrong with including eventfd.h before err.h, so the easiest fix is to make it possible to do this by including the file where it is needed. Link: http://lkml.kernel.org/r/20180724110737.3985088-1-arnd@arndb.de Fixes: 9a69f5087ccc ("drivers/staging: Gasket driver framework + Apex driver") Signed-off-by: Arnd Bergmann Cc: Eric Biggers Cc: Al Viro Cc: Greg Kroah-Hartman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

eventfd: fold eventfd_ctx_get() into eventfd_ctx_fileget()

2018-01-06T18:47:20Z

eventfd_ctx_get() is not used outside of eventfd.c, so unexport it and fold it into eventfd_ctx_fileget(). (eventfd_ctx_get() was apparently added years ago for KVM irqfd's, but was never used.) Signed-off-by: Eric Biggers Signed-off-by: Al Viro

eventfd: fold eventfd_ctx_read() into eventfd_read()

2018-01-06T18:47:20Z

eventfd_ctx_read() is not used outside of eventfd.c, so unexport it and fold it into eventfd_read(). This slightly simplifies the code and makes it more analogous to eventfd_write(). (eventfd_ctx_read() was apparently added years ago for KVM irqfd's, but was never used.) Signed-off-by: Eric Biggers Signed-off-by: Al Viro

eventfd: convert to use anon_inode_getfd()

2018-01-06T18:47:20Z

Nothing actually calls eventfd_file_create() besides the eventfd2() system call itself. So simplify things by folding it into the system call and using anon_inode_getfd() instead of anon_inode_getfile(). This removes over 40 lines with no change in functionality. (eventfd_file_create() was apparently added years ago for KVM irqfd's, but was never used.) Signed-off-by: Eric Biggers Signed-off-by: Al Viro