On Sun, Oct 11 2009, Michael Schmitz wrote:
Hi Geert,There is a nice gem in drivers/block/ataflop.c::do_fd_request() void do_fd_request(struct request_queue * q) { unsigned long flags; DPRINT(("do_fd_request for pid %d\n",current->pid)); while( fdc_busy ) sleep_on( &fdc_wait ); fdc_busy = 1; stdma_lock(floppy_irq, NULL); atari_disable_irq( IRQ_MFP_FDC ); local_save_flags(flags); /* The request function is called with ints local_irq_disable(); * disabled... so must save the IPL for later */ redo_fd_request(); local_irq_restore(flags); atari_enable_irq( IRQ_MFP_FDC ); } If you look at the code long enough, you will notioce that the local_irq_disable() call is actually commented out. This has been introduced back in 2002 in [1], but as you can see, the same bug has been there even before, with the sti() call being commented out in the very same way :) I am not familiar with the code myself at all, but I guess that the whole stuff can just be removed. Why do we need save_flags/restore_flags at all, without actually disabling the local IRQs afterwards? TheThe IRQ source has been disabled in the MFC by the atari_disable_irq( IRQ_MFP_FDC ) call just before local_save_flags(flags). For that reason, the fact that local_irq_disable is commented out will not usually matter (a timer interrupt that would result in retrying the floppy request or removing the request from the queue excepted). I would rather suggest to leave the code in, and fix the buggy comments instead.
What buggy comments? The comments states that interrupts are already disabled when entering this function, which is correct. The point is that doing a flags save and then an irq disable is pointless, since we KNOW that interrupts are already disabled. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-m68k" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
