From 0c2bd9b24e73287aa4ee87844c847205e0da8a9b Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Thu, 3 Mar 2011 17:56:07 +0100 Subject: [S390] tape: deadlock on system work queue The 34xx and 3590 tape driver uses the system work queue to defer work from the interrupt function to process context, e.g. a medium sense after an unsolicited interrupt. The tape commands started by the work handler need to be asynchronous, otherwise a deadlock on the system work queue can occur. Signed-off-by: Martin Schwidefsky --- drivers/s390/char/tape_34xx.c | 59 ++++++++++++++++++++++++++++++------------- 1 file changed, 41 insertions(+), 18 deletions(-) (limited to 'drivers/s390/char/tape_34xx.c') diff --git a/drivers/s390/char/tape_34xx.c b/drivers/s390/char/tape_34xx.c index c17f35b6136a..c26511171ffe 100644 --- a/drivers/s390/char/tape_34xx.c +++ b/drivers/s390/char/tape_34xx.c @@ -53,23 +53,11 @@ static void tape_34xx_delete_sbid_from(struct tape_device *, int); * Medium sense for 34xx tapes. There is no 'real' medium sense call. * So we just do a normal sense. */ -static int -tape_34xx_medium_sense(struct tape_device *device) +static void __tape_34xx_medium_sense(struct tape_request *request) { - struct tape_request *request; - unsigned char *sense; - int rc; - - request = tape_alloc_request(1, 32); - if (IS_ERR(request)) { - DBF_EXCEPTION(6, "MSEN fail\n"); - return PTR_ERR(request); - } - - request->op = TO_MSEN; - tape_ccw_end(request->cpaddr, SENSE, 32, request->cpdata); + struct tape_device *device = request->device; + unsigned char *sense; - rc = tape_do_io_interruptible(device, request); if (request->rc == 0) { sense = request->cpdata; @@ -88,15 +76,47 @@ tape_34xx_medium_sense(struct tape_device *device) device->tape_generic_status |= GMT_WR_PROT(~0); else device->tape_generic_status &= ~GMT_WR_PROT(~0); - } else { + } else DBF_EVENT(4, "tape_34xx: medium sense failed with rc=%d\n", request->rc); - } tape_free_request(request); +} + +static int tape_34xx_medium_sense(struct tape_device *device) +{ + struct tape_request *request; + int rc; + + request = tape_alloc_request(1, 32); + if (IS_ERR(request)) { + DBF_EXCEPTION(6, "MSEN fail\n"); + return PTR_ERR(request); + } + request->op = TO_MSEN; + tape_ccw_end(request->cpaddr, SENSE, 32, request->cpdata); + rc = tape_do_io_interruptible(device, request); + __tape_34xx_medium_sense(request); return rc; } +static void tape_34xx_medium_sense_async(struct tape_device *device) +{ + struct tape_request *request; + + request = tape_alloc_request(1, 32); + if (IS_ERR(request)) { + DBF_EXCEPTION(6, "MSEN fail\n"); + return; + } + + request->op = TO_MSEN; + tape_ccw_end(request->cpaddr, SENSE, 32, request->cpdata); + request->callback = (void *) __tape_34xx_medium_sense; + request->callback_data = NULL; + tape_do_io_async(device, request); +} + struct tape_34xx_work { struct tape_device *device; enum tape_op op; @@ -109,6 +129,9 @@ struct tape_34xx_work { * is inserted but cannot call tape_do_io* from an interrupt context. * Maybe that's useful for other actions we want to start from the * interrupt handler. + * Note: the work handler is called by the system work queue. The tape + * commands started by the handler need to be asynchrounous, otherwise + * a deadlock can occur e.g. in case of a deferred cc=1 (see __tape_do_irq). */ static void tape_34xx_work_handler(struct work_struct *work) @@ -119,7 +142,7 @@ tape_34xx_work_handler(struct work_struct *work) switch(p->op) { case TO_MSEN: - tape_34xx_medium_sense(device); + tape_34xx_medium_sense_async(device); break; default: DBF_EVENT(3, "T34XX: internal error: unknown work\n"); -- cgit v1.2.3