偷得浮生半桶水(半日闲), 好记性不如抄下来(烂笔头). 信息爆炸的时代, 学习是一项持续的工作.
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分类: LINUX
2009-02-06 17:29:48
struct globalvar_dev { int global_var = 0; struct semaphore sem; wait_queue_head_t outq; int flag = 0; }; open()和release() |
int scull_u_open(struct inode *inode, struct file *filp) { Scull_Dev *dev = &scull_u_device; /* device information */ int num = NUM(inode->i_rdev); if (!filp->private_data && num > 0) return -ENODEV; /* not devfs: allow 1 device only */ spin_lock(&scull_u_lock); if (scull_u_count && (scull_u_owner != current->uid) && /* allow user */ (scull_u_owner != current->euid) && /* allow whoever did su */ !capable(CAP_DAC_OVERRIDE)) { /* still allow root */ spin_unlock(&scull_u_lock); return -EBUSY; /* -EPERM would confuse the user */ } if (scull_u_count == 0) scull_u_owner = current->uid; /* grab it */ scull_u_count++; spin_unlock(&scull_u_lock); /* then, everything else is copied from the bare scull device */ if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) scull_trim(dev); if (!filp->private_data) filp->private_data = dev; MOD_INC_USE_COUNT; return 0; /* success */ } int scull_u_release(struct inode *inode, struct file *filp) { scull_u_count--; /* nothing else */ MOD_DEC_USE_COUNT; return 0; } |