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[S390] tape: deadlock on system work queue
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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 <schwidefsky@de.ibm.com>
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Martin Schwidefsky authored and Martin Schwidefsky committed Mar 3, 2011
1 parent b652277 commit 0c2bd9b
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Showing 3 changed files with 116 additions and 34 deletions.
8 changes: 8 additions & 0 deletions drivers/s390/char/tape.h
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Original file line number Diff line number Diff line change
Expand Up @@ -280,6 +280,14 @@ tape_do_io_free(struct tape_device *device, struct tape_request *request)
return rc;
}

static inline void
tape_do_io_async_free(struct tape_device *device, struct tape_request *request)
{
request->callback = (void *) tape_free_request;
request->callback_data = NULL;
tape_do_io_async(device, request);
}

extern int tape_oper_handler(int irq, int status);
extern void tape_noper_handler(int irq, int status);
extern int tape_open(struct tape_device *);
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59 changes: 41 additions & 18 deletions drivers/s390/char/tape_34xx.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;

Expand All @@ -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;
Expand All @@ -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)
Expand All @@ -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");
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83 changes: 67 additions & 16 deletions drivers/s390/char/tape_3590.c
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Original file line number Diff line number Diff line change
Expand Up @@ -329,17 +329,17 @@ static int tape_3592_ioctl_kekl_set(struct tape_device *device,
/*
* Enable encryption
*/
static int tape_3592_enable_crypt(struct tape_device *device)
static struct tape_request *__tape_3592_enable_crypt(struct tape_device *device)
{
struct tape_request *request;
char *data;

DBF_EVENT(6, "tape_3592_enable_crypt\n");
if (!crypt_supported(device))
return -ENOSYS;
return ERR_PTR(-ENOSYS);
request = tape_alloc_request(2, 72);
if (IS_ERR(request))
return PTR_ERR(request);
return request;
data = request->cpdata;
memset(data,0,72);

Expand All @@ -354,23 +354,42 @@ static int tape_3592_enable_crypt(struct tape_device *device)
request->op = TO_CRYPT_ON;
tape_ccw_cc(request->cpaddr, MODE_SET_CB, 36, data);
tape_ccw_end(request->cpaddr + 1, MODE_SET_CB, 36, data + 36);
return request;
}

static int tape_3592_enable_crypt(struct tape_device *device)
{
struct tape_request *request;

request = __tape_3592_enable_crypt(device);
if (IS_ERR(request))
return PTR_ERR(request);
return tape_do_io_free(device, request);
}

static void tape_3592_enable_crypt_async(struct tape_device *device)
{
struct tape_request *request;

request = __tape_3592_enable_crypt(device);
if (!IS_ERR(request))
tape_do_io_async_free(device, request);
}

/*
* Disable encryption
*/
static int tape_3592_disable_crypt(struct tape_device *device)
static struct tape_request *__tape_3592_disable_crypt(struct tape_device *device)
{
struct tape_request *request;
char *data;

DBF_EVENT(6, "tape_3592_disable_crypt\n");
if (!crypt_supported(device))
return -ENOSYS;
return ERR_PTR(-ENOSYS);
request = tape_alloc_request(2, 72);
if (IS_ERR(request))
return PTR_ERR(request);
return request;
data = request->cpdata;
memset(data,0,72);

Expand All @@ -383,9 +402,28 @@ static int tape_3592_disable_crypt(struct tape_device *device)
tape_ccw_cc(request->cpaddr, MODE_SET_CB, 36, data);
tape_ccw_end(request->cpaddr + 1, MODE_SET_CB, 36, data + 36);

return request;
}

static int tape_3592_disable_crypt(struct tape_device *device)
{
struct tape_request *request;

request = __tape_3592_disable_crypt(device);
if (IS_ERR(request))
return PTR_ERR(request);
return tape_do_io_free(device, request);
}

static void tape_3592_disable_crypt_async(struct tape_device *device)
{
struct tape_request *request;

request = __tape_3592_disable_crypt(device);
if (!IS_ERR(request))
tape_do_io_async_free(device, request);
}

/*
* IOCTL: Set encryption status
*/
Expand Down Expand Up @@ -457,8 +495,7 @@ tape_3590_ioctl(struct tape_device *device, unsigned int cmd, unsigned long arg)
/*
* SENSE Medium: Get Sense data about medium state
*/
static int
tape_3590_sense_medium(struct tape_device *device)
static int tape_3590_sense_medium(struct tape_device *device)
{
struct tape_request *request;

Expand All @@ -470,6 +507,18 @@ tape_3590_sense_medium(struct tape_device *device)
return tape_do_io_free(device, request);
}

static void tape_3590_sense_medium_async(struct tape_device *device)
{
struct tape_request *request;

request = tape_alloc_request(1, 128);
if (IS_ERR(request))
return;
request->op = TO_MSEN;
tape_ccw_end(request->cpaddr, MEDIUM_SENSE, 128, request->cpdata);
tape_do_io_async_free(device, request);
}

/*
* MTTELL: Tell block. Return the number of block relative to current file.
*/
Expand Down Expand Up @@ -546,28 +595,30 @@ tape_3590_read_opposite(struct tape_device *device,
* 2. The attention msg is written to the "read subsystem data" buffer.
* In this case we probably should print it to the console.
*/
static int
tape_3590_read_attmsg(struct tape_device *device)
static void tape_3590_read_attmsg_async(struct tape_device *device)
{
struct tape_request *request;
char *buf;

request = tape_alloc_request(3, 4096);
if (IS_ERR(request))
return PTR_ERR(request);
return;
request->op = TO_READ_ATTMSG;
buf = request->cpdata;
buf[0] = PREP_RD_SS_DATA;
buf[6] = RD_ATTMSG; /* read att msg */
tape_ccw_cc(request->cpaddr, PERFORM_SS_FUNC, 12, buf);
tape_ccw_cc(request->cpaddr + 1, READ_SS_DATA, 4096 - 12, buf + 12);
tape_ccw_end(request->cpaddr + 2, NOP, 0, NULL);
return tape_do_io_free(device, request);
tape_do_io_async_free(device, request);
}

/*
* These functions are used to schedule follow-up actions from within an
* interrupt context (like unsolicited interrupts).
* 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).
*/
struct work_handler_data {
struct tape_device *device;
Expand All @@ -583,16 +634,16 @@ tape_3590_work_handler(struct work_struct *work)

switch (p->op) {
case TO_MSEN:
tape_3590_sense_medium(p->device);
tape_3590_sense_medium_async(p->device);
break;
case TO_READ_ATTMSG:
tape_3590_read_attmsg(p->device);
tape_3590_read_attmsg_async(p->device);
break;
case TO_CRYPT_ON:
tape_3592_enable_crypt(p->device);
tape_3592_enable_crypt_async(p->device);
break;
case TO_CRYPT_OFF:
tape_3592_disable_crypt(p->device);
tape_3592_disable_crypt_async(p->device);
break;
default:
DBF_EVENT(3, "T3590: work handler undefined for "
Expand Down

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