down_interruptible() return non-zero value once signal is received and trying down_interruptible again in loop return value is always non-zero

Oct. 18, 2013

      Hi,

In kernel driver, using Semaphore to block on resources (Descriptors and
memory).
Semaphore is initialized in locking state using call "init_MTEX_LOCKED()",
when resources are not available process calls down_interruptible() and
blocks. Once resources are freed up() is called, and blocked process is
unblocked. up() is called from interrupt context which frees resources on
receiving ACK-Interrupt.
Following is the code snippet for blocking:
do {
    ret = down_interruptible(sem)
    if (ret == 0) {
        break;
    } else {
        printk("Semaphore is not acquired try again\n");
        continue;
   }
} while (1);

While loop is used to make sure down_interrptible() is called until process
acquires the semaphore. If process receives signal, process unblocks from
down_interrptible() without acquiring the semaphore.
Issue am seeing is once signal is received under the blocking state, again
trying to acquire semaphore using down_interruptible() return value is
always non-zero and process is looping in while loop.

Can someone explain this behavior, I wrote the code with expectation that
after signal is received again trying to acquire lock will either block the
process or process will get semaphore.
Please help me on this.

Thanks,
Mushtaq Khan