From b15624b39b9b19ba139776e2a917bcd4e361c01e Mon Sep 17 00:00:00 2001 From: Alex Waterman Date: Wed, 15 Aug 2018 16:32:37 -0700 Subject: gpu: nvgpu: posix: move the posix dir to os Since the posix code is supporting a particular OS this code should belong under os/ not common/. Change-Id: Idf5f75b8ab9d614c9dd43ea23dab8df3c346c0ef Signed-off-by: Alex Waterman Reviewed-on: https://git-master.nvidia.com/r/1800658 Reviewed-by: mobile promotions Tested-by: mobile promotions --- drivers/gpu/nvgpu/os/posix/rwsem.c | 117 +++++++++++++++++++++++++++++++++++++ 1 file changed, 117 insertions(+) create mode 100644 drivers/gpu/nvgpu/os/posix/rwsem.c (limited to 'drivers/gpu/nvgpu/os/posix/rwsem.c') diff --git a/drivers/gpu/nvgpu/os/posix/rwsem.c b/drivers/gpu/nvgpu/os/posix/rwsem.c new file mode 100644 index 00000000..7a696b75 --- /dev/null +++ b/drivers/gpu/nvgpu/os/posix/rwsem.c @@ -0,0 +1,117 @@ +/* + * Copyright (c) 2018, NVIDIA CORPORATION. All rights reserved. + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER + * DEALINGS IN THE SOFTWARE. + */ + +#include +#include +#include + +#include + +void nvgpu_rwsem_init(struct nvgpu_rwsem *rwsem) +{ + memset(rwsem, 0, sizeof(*rwsem)); + + nvgpu_spinlock_init(&rwsem->lock); +} + +/* + * Acquire. + */ +void nvgpu_rwsem_down_read(struct nvgpu_rwsem *rwsem) +{ + while (true) { + nvgpu_spinlock_acquire(&rwsem->lock); + + /* + * If there's a writer try again. + */ + if (rwsem->writers < 0) { + nvgpu_spinlock_release(&rwsem->lock); + nvgpu_msleep(10); + continue; + } + + /* + * Otherwise decrement the read counter and return. + */ + rwsem->readers -= 1; + nvgpu_spinlock_release(&rwsem->lock); + return; + } +} + +/* + * Release. + */ +void nvgpu_rwsem_up_read(struct nvgpu_rwsem *rwsem) +{ + nvgpu_spinlock_acquire(&rwsem->lock); + rwsem->readers += 1; + + /* + * Can't be any writers if there was a reader. Also can't be + * a positive number of readers. The increments are always + * downward so if we have a positive number then there is a + * balancing bug. + */ + BUG_ON(rwsem->writers < 0); + BUG_ON(rwsem->readers > 0); + + nvgpu_spinlock_release(&rwsem->lock); +} + +void nvgpu_rwsem_down_write(struct nvgpu_rwsem *rwsem) +{ + while (true) { + nvgpu_spinlock_acquire(&rwsem->lock); + + /* + * If there's a reader or a writer try again. Note: in this very + * simple implementation it's possible for readers to + * indefinitely starve writers. + */ + if (rwsem->writers < 0 || rwsem->readers < 0) { + nvgpu_spinlock_release(&rwsem->lock); + nvgpu_msleep(10); + continue; + } + + rwsem->writers -= 1; + nvgpu_spinlock_release(&rwsem->lock); + return; + } +} + +void nvgpu_rwsem_up_write(struct nvgpu_rwsem *rwsem) +{ + nvgpu_spinlock_acquire(&rwsem->lock); + rwsem->writers += 1; + + /* + * Writers can't be positive: that would be an unbalanced free. Readers + * must be zero - otherwise this writer should never have had access! + */ + BUG_ON(rwsem->writers > 0); + BUG_ON(rwsem->readers != 0); + + nvgpu_spinlock_release(&rwsem->lock); +} -- cgit v1.2.2