/* * Sample kfifo byte stream implementation * * Copyright (C) 2010 Stefani Seibold * * Released under the GPL version 2 only. * */ #include #include #include #include #include /* * This module shows how to create a byte stream fifo. */ /* fifo size in elements (bytes) */ #define FIFO_SIZE 32 /* name of the proc entry */ #define PROC_FIFO "bytestream-fifo" /* lock for procfs read access */ static DEFINE_MUTEX(read_lock); /* lock for procfs write access */ static DEFINE_MUTEX(write_lock); /* * define DYNAMIC in this example for a dynamically allocated fifo. * * Otherwise the fifo storage will be a part of the fifo structure. */ #if 0 #define DYNAMIC #endif #ifdef DYNAMIC static struct kfifo test; #else static DECLARE_KFIFO(test, unsigned char, FIFO_SIZE); #endif static const unsigned char expected_result[FIFO_SIZE] = { 3, 4, 5, 6, 7, 8, 9, 0, 1, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, }; static int __init testfunc(void) { unsigned char buf[6]; unsigned char i, j; unsigned int ret; printk(KERN_INFO "byte stream fifo test start\n"); /* put string into the fifo */ kfifo_in(&test, "hello", 5); /* put values into the fifo */ for (i = 0; i != 10; i++) kfifo_put(&test, i); /* show the number of used elements */ printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test)); /* get max of 5 bytes from the fifo */ i = kfifo_out(&test, buf, 5); printk(KERN_INFO "buf: %.*s\n", i, buf); /* get max of 2 elements from the fifo */ ret = kfifo_out(&test, buf, 2); printk(KERN_INFO "ret: %d\n", ret); /* and put it back to the end of the fifo */ ret = kfifo_in(&test, buf, ret); printk(KERN_INFO "ret: %d\n", ret); /* skip first element of the fifo */ printk(KERN_INFO "skip 1st element\n"); kfifo_skip(&test); /* put values into the fifo until is full */ for (i = 20; kfifo_put(&test, i); i++) ; printk(KERN_INFO "queue len: %u\n", kfifo_len(&test)); /* show the first value without removing from the fifo */ if (kfifo_peek(&test, &i)) printk(KERN_INFO "%d\n", i); /* check the correctness of all values in the fifo */ j = 0; while (kfifo_get(&test, &i)) { printk(KERN_INFO "item = %d\n", i); if (i != expected_result[j++]) { printk(KERN_WARNING "value mismatch: test failed\n"); return -EIO; } } if (j != ARRAY_SIZE(expected_result)) { printk(KERN_WARNING "size mismatch: test failed\n"); return -EIO; } printk(KERN_INFO "test passed\n"); return 0; } static ssize_t fifo_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { int ret; unsigned int copied; if (mutex_lock_interruptible(&write_lock)) return -ERESTARTSYS; ret = kfifo_from_user(&test, buf, count, &copied); mutex_unlock(&write_lock); return ret ? ret : copied; } static ssize_t fifo_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { int ret; unsigned int copied; if (mutex_lock_interruptible(&read_lock)) return -ERESTARTSYS; ret = kfifo_to_user(&test, buf, count, &copied); mutex_unlock(&read_lock); return ret ? ret : copied; } static const struct file_operations fifo_fops = { .owner = THIS_MODULE, .read = fifo_read, .write = fifo_write, .llseek = noop_llseek, }; static int __init example_init(void) { #ifdef DYNAMIC int ret; ret = kfifo_alloc(&test, FIFO_SIZE, GFP_KERNEL); if (ret) { printk(KERN_ERR "error kfifo_alloc\n"); return ret; } #else INIT_KFIFO(test); #endif if (testfunc() < 0) { #ifdef DYNAMIC kfifo_free(&test); #endif return -EIO; } if (proc_create(PROC_FIFO, 0, NULL, &fifo_fops) == NULL) { #ifdef DYNAMIC kfifo_free(&test); #endif return -ENOMEM; } return 0; } static void __exit example_exit(void) { remove_proc_entry(PROC_FIFO, NULL); #ifdef DYNAMIC kfifo_free(&test); #endif } module_init(example_init); module_exit(example_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Stefani Seibold "); 'ignorews' onchange='this.form.submit();'>mode:
authorIago Abal <mail@iagoabal.eu>2017-01-11 14:00:21 +0100
committerVinod Koul <vinod.koul@intel.com>2017-01-25 15:35:11 +0530
commit91539eb1fda2d530d3b268eef542c5414e54bf1a (patch)
tree960f5ca6342ad20837aff18aad6e8ecd7da32fd6 /tools/arch/s390/include
parent6610d0edf6dc7ee97e46ab3a538a565c79d26199 (diff)
dmaengine: pl330: fix double lock
The static bug finder EBA (http://www.iagoabal.eu/eba/) reported the following double-lock bug: Double lock: 1. spin_lock_irqsave(pch->lock, flags) at pl330_free_chan_resources:2236; 2. call to function `pl330_release_channel' immediately after; 3. call to function `dma_pl330_rqcb' in line 1753; 4. spin_lock_irqsave(pch->lock, flags) at dma_pl330_rqcb:1505. I have fixed it as suggested by Marek Szyprowski. First, I have replaced `pch->lock' with `pl330->lock' in functions `pl330_alloc_chan_resources' and `pl330_free_chan_resources'. This avoids the double-lock by acquiring a different lock than `dma_pl330_rqcb'. NOTE that, as a result, `pl330_free_chan_resources' executes `list_splice_tail_init' on `pch->work_list' under lock `pl330->lock', whereas in the rest of the code `pch->work_list' is protected by `pch->lock'. I don't know if this may cause race conditions. Similarly `pch->cyclic' is written by `pl330_alloc_chan_resources' under `pl330->lock' but read by `pl330_tx_submit' under `pch->lock'. Second, I have removed locking from `pl330_request_channel' and `pl330_release_channel' functions. Function `pl330_request_channel' is only called from `pl330_alloc_chan_resources', so the lock is already held. Function `pl330_release_channel' is called from `pl330_free_chan_resources', which already holds the lock, and from `pl330_del'. Function `pl330_del' is called in an error path of `pl330_probe' and at the end of `pl330_remove', but I assume that there cannot be concurrent accesses to the protected data at those points. Signed-off-by: Iago Abal <mail@iagoabal.eu> Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Diffstat (limited to 'tools/arch/s390/include')