From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH] io_uring: use __kernel_timespec in timeout ABI Date: Tue, 1 Oct 2019 09:38:40 -0600 Message-ID: <623e1d27-d3b1-3241-bfd4-eb94ce70da14@kernel.dk> References: <20190930202055.1748710-1-arnd@arndb.de> <8d5d34da-e1f0-1ab5-461e-f3145e52c48a@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <8d5d34da-e1f0-1ab5-461e-f3145e52c48a@kernel.dk> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Arnd Bergmann Cc: y2038@lists.linaro.org, linux-api@vger.kernel.org, Alexander Viro , =?UTF-8?Q?Stefan_B=c3=bchler?= , Hannes Reinecke , Jackie Liu , Andrew Morton , Hristo Venev , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-api@vger.kernel.org On 10/1/19 8:09 AM, Jens Axboe wrote: > On 9/30/19 2:20 PM, Arnd Bergmann wrote: >> All system calls use struct __kernel_timespec instead of the old struct >> timespec, but this one was just added with the old-style ABI. Change it >> now to enforce the use of __kernel_timespec, avoiding ABI confusion and >> the need for compat handlers on 32-bit architectures. >> >> Any user space caller will have to use __kernel_timespec now, but this >> is unambiguous and works for any C library regardless of the time_t >> definition. A nicer way to specify the timeout would have been a less >> ambiguous 64-bit nanosecond value, but I suppose it's too late now to >> change that as this would impact both 32-bit and 64-bit users. > > Thanks for catching that, Arnd. Applied. On second thought - since there appears to be no good 64-bit timespec available to userspace, the alternative here is including on in liburing. That seems kinda crappy in terms of API, so why not just use a 64-bit nsec value as you suggest? There's on released kernel with this feature yet, so there's nothing stopping us from just changing the API to be based on a single 64-bit nanosecond timeout. diff --git a/fs/io_uring.c b/fs/io_uring.c index dd094b387cab..de3d14fe3025 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1892,16 +1892,13 @@ static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe) unsigned count, req_dist, tail_index; struct io_ring_ctx *ctx = req->ctx; struct list_head *entry; - struct timespec ts; + u64 timeout; if (unlikely(ctx->flags & IORING_SETUP_IOPOLL)) return -EINVAL; if (sqe->flags || sqe->ioprio || sqe->buf_index || sqe->timeout_flags || sqe->len != 1) return -EINVAL; - if (copy_from_user(&ts, (void __user *) (unsigned long) sqe->addr, - sizeof(ts))) - return -EFAULT; /* * sqe->off holds how many events that need to occur for this @@ -1932,9 +1929,10 @@ static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe) list_add(&req->list, entry); spin_unlock_irq(&ctx->completion_lock); + timeout = READ_ONCE(sqe->addr); hrtimer_init(&req->timeout.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); req->timeout.timer.function = io_timeout_fn; - hrtimer_start(&req->timeout.timer, timespec_to_ktime(ts), + hrtimer_start(&req->timeout.timer, ns_to_ktime(timeout), HRTIMER_MODE_REL); return 0; } -- Jens Axboe