Hi I am working on fedora core 7, kernel version 2.6.21, gcc version 4.1.2. I have my user space application which communicate with my char driver using write and read system calls. I have a thread in application to send data to driver and concurrently a signal handler(user space) is register. write calls is invoking continuously and read call is also invoking continuously on notification from driver. Here am facing a problem of "futex_wait" at one time. Even though my user space application has no mutex locking, FUTEX_WAIT is called and nothing proceeds after this. I got below lines form strace of my process and always getting lock at same address. --- SIGRT_15 (Real-time signal 13) @ 0 (0) --- futex(0x4aa700b0, FUTEX_WAIT, 2, NULL please give me some tips to solve this issue or what could be reason for above things. if need any more info, i will give u. thanks... regards, pandi.k