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linux/drivers/s390/char/raw3270.h
Guilherme G. Piccoli 4ae46db99c s390/consoles: improve panic notifiers reliability 
Currently many console drivers for s390 rely on panic/reboot notifiers
to invoke callbacks on these events. The panic() function disables local
IRQs, secondary CPUs and preemption, so callbacks invoked on panic are
effectively running in atomic context.

Happens that most of these console callbacks from s390 doesn't take the
proper care with regards to atomic context, like taking spinlocks that
might be taken in other function/CPU and hence will cause a lockup
situation.

The goal for this patch is to improve the notifiers reliability, acting
on 4 console drivers, as detailed below:

(1) con3215: changed a regular spinlock to the trylock alternative.

(2) con3270: also changed a regular spinlock to its trylock counterpart,
but here we also have another problem: raw3270_activate_view() takes a
different spinlock. So, we worked a helper to validate if this other lock
is safe to acquire, and if so, raw3270_activate_view() should be safe.

Notice though that there is a functional change here: it's now possible
to continue the notifier code [reaching con3270_wait_write() and
con3270_rebuild_update()] without executing raw3270_activate_view().

(3) sclp: a global lock is used heavily in the functions called from
the notifier, so we added a check here - if the lock is taken already,
we just bail-out, preventing the lockup.

(4) sclp_vt220: same as (3), a lock validation was added to prevent the
potential lockup problem.

Besides (1)-(4), we also removed useless void functions, adding the
code called from the notifier inside its own body, and changed the
priority of such notifiers to execute late, since they are "heavyweight"
for the panic environment, so we aim to reduce risks here.
Changed return values to NOTIFY_DONE as well, the standard one.

Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Link: https://lore.kernel.org/r/20220427224924.592546-14-gpiccoli@igalia.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
2022-05-06 20:45:13 +02:00

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/* SPDX-License-Identifier: GPL-2.0 */
/*
* IBM/3270 Driver
*
* Author(s):
* Original 3270 Code for 2.4 written by Richard Hitt (UTS Global)
* Rewritten for 2.5 by Martin Schwidefsky <schwidefsky@de.ibm.com>
* Copyright IBM Corp. 2003, 2009
*/
#include <asm/idals.h>
#include <asm/ioctl.h>
/* ioctls for fullscreen 3270 */
#define TUBICMD _IO('3', 3) /* set ccw command for fs reads. */
#define TUBOCMD _IO('3', 4) /* set ccw command for fs writes. */
#define TUBGETI _IO('3', 7) /* get ccw command for fs reads. */
#define TUBGETO _IO('3', 8) /* get ccw command for fs writes. */
#define TUBSETMOD _IO('3',12) /* FIXME: what does it do ?*/
#define TUBGETMOD _IO('3',13) /* FIXME: what does it do ?*/
/* Local Channel Commands */
#define TC_WRITE 0x01 /* Write */
#define TC_RDBUF 0x02 /* Read Buffer */
#define TC_EWRITE 0x05 /* Erase write */
#define TC_READMOD 0x06 /* Read modified */
#define TC_EWRITEA 0x0d /* Erase write alternate */
#define TC_WRITESF 0x11 /* Write structured field */
/* Buffer Control Orders */
#define TO_SF 0x1d /* Start field */
#define TO_SBA 0x11 /* Set buffer address */
#define TO_IC 0x13 /* Insert cursor */
#define TO_PT 0x05 /* Program tab */
#define TO_RA 0x3c /* Repeat to address */
#define TO_SFE 0x29 /* Start field extended */
#define TO_EUA 0x12 /* Erase unprotected to address */
#define TO_MF 0x2c /* Modify field */
#define TO_SA 0x28 /* Set attribute */
/* Field Attribute Bytes */
#define TF_INPUT 0x40 /* Visible input */
#define TF_INPUTN 0x4c /* Invisible input */
#define TF_INMDT 0xc1 /* Visible, Set-MDT */
#define TF_LOG 0x60
/* Character Attribute Bytes */
#define TAT_RESET 0x00
#define TAT_FIELD 0xc0
#define TAT_EXTHI 0x41
#define TAT_COLOR 0x42
#define TAT_CHARS 0x43
#define TAT_TRANS 0x46
/* Extended-Highlighting Bytes */
#define TAX_RESET 0x00
#define TAX_BLINK 0xf1
#define TAX_REVER 0xf2
#define TAX_UNDER 0xf4
/* Reset value */
#define TAR_RESET 0x00
/* Color values */
#define TAC_RESET 0x00
#define TAC_BLUE 0xf1
#define TAC_RED 0xf2
#define TAC_PINK 0xf3
#define TAC_GREEN 0xf4
#define TAC_TURQ 0xf5
#define TAC_YELLOW 0xf6
#define TAC_WHITE 0xf7
#define TAC_DEFAULT 0x00
/* Write Control Characters */
#define TW_NONE 0x40 /* No particular action */
#define TW_KR 0xc2 /* Keyboard restore */
#define TW_PLUSALARM 0x04 /* Add this bit for alarm */
#define RAW3270_FIRSTMINOR 1 /* First minor number */
#define RAW3270_MAXDEVS 255 /* Max number of 3270 devices */
/* For TUBGETMOD and TUBSETMOD. Should include. */
struct raw3270_iocb {
short model;
short line_cnt;
short col_cnt;
short pf_cnt;
short re_cnt;
short map;
};
struct raw3270;
struct raw3270_view;
extern struct class *class3270;
/* 3270 CCW request */
struct raw3270_request {
struct list_head list; /* list head for request queueing. */
struct raw3270_view *view; /* view of this request */
struct ccw1 ccw; /* single ccw. */
void *buffer; /* output buffer. */
size_t size; /* size of output buffer. */
int rescnt; /* residual count from devstat. */
int rc; /* return code for this request. */
/* Callback for delivering final status. */
void (*callback)(struct raw3270_request *, void *);
void *callback_data;
};
struct raw3270_request *raw3270_request_alloc(size_t size);
void raw3270_request_free(struct raw3270_request *);
void raw3270_request_reset(struct raw3270_request *);
void raw3270_request_set_cmd(struct raw3270_request *, u8 cmd);
int raw3270_request_add_data(struct raw3270_request *, void *, size_t);
void raw3270_request_set_data(struct raw3270_request *, void *, size_t);
void raw3270_request_set_idal(struct raw3270_request *, struct idal_buffer *);
static inline int
raw3270_request_final(struct raw3270_request *rq)
{
return list_empty(&rq->list);
}
void raw3270_buffer_address(struct raw3270 *, char *, unsigned short);
/*
* Functions of a 3270 view.
*/
struct raw3270_fn {
int (*activate)(struct raw3270_view *);
void (*deactivate)(struct raw3270_view *);
void (*intv)(struct raw3270_view *,
struct raw3270_request *, struct irb *);
void (*release)(struct raw3270_view *);
void (*free)(struct raw3270_view *);
void (*resize)(struct raw3270_view *, int, int, int);
};
/*
* View structure chaining. The raw3270_view structure is meant to
* be embedded at the start of the real view data structure, e.g.:
* struct example {
* struct raw3270_view view;
* ...
* };
*/
struct raw3270_view {
struct list_head list;
spinlock_t lock;
#define RAW3270_VIEW_LOCK_IRQ 0
#define RAW3270_VIEW_LOCK_BH 1
atomic_t ref_count;
struct raw3270 *dev;
struct raw3270_fn *fn;
unsigned int model;
unsigned int rows, cols; /* # of rows & colums of the view */
unsigned char *ascebc; /* ascii -> ebcdic table */
};
int raw3270_add_view(struct raw3270_view *, struct raw3270_fn *, int, int);
int raw3270_view_lock_unavailable(struct raw3270_view *view);
int raw3270_activate_view(struct raw3270_view *);
void raw3270_del_view(struct raw3270_view *);
void raw3270_deactivate_view(struct raw3270_view *);
struct raw3270_view *raw3270_find_view(struct raw3270_fn *, int);
int raw3270_start(struct raw3270_view *, struct raw3270_request *);
int raw3270_start_locked(struct raw3270_view *, struct raw3270_request *);
int raw3270_start_irq(struct raw3270_view *, struct raw3270_request *);
int raw3270_reset(struct raw3270_view *);
struct raw3270_view *raw3270_view(struct raw3270_view *);
int raw3270_view_active(struct raw3270_view *);
/* Reference count inliner for view structures. */
static inline void
raw3270_get_view(struct raw3270_view *view)
{
atomic_inc(&view->ref_count);
}
extern wait_queue_head_t raw3270_wait_queue;
static inline void
raw3270_put_view(struct raw3270_view *view)
{
if (atomic_dec_return(&view->ref_count) == 0)
wake_up(&raw3270_wait_queue);
}
struct raw3270 *raw3270_setup_console(void);
void raw3270_wait_cons_dev(struct raw3270 *);
/* Notifier for device addition/removal */
struct raw3270_notifier {
struct list_head list;
void (*create)(int minor);
void (*destroy)(int minor);
};
int raw3270_register_notifier(struct raw3270_notifier *);
void raw3270_unregister_notifier(struct raw3270_notifier *);
/*
* Little memory allocator for string objects.
*/
struct string
{
struct list_head list;
struct list_head update;
unsigned long size;
unsigned long len;
char string[];
} __attribute__ ((aligned(8)));
static inline struct string *
alloc_string(struct list_head *free_list, unsigned long len)
{
struct string *cs, *tmp;
unsigned long size;
size = (len + 7L) & -8L;
list_for_each_entry(cs, free_list, list) {
if (cs->size < size)
continue;
if (cs->size > size + sizeof(struct string)) {
char *endaddr = (char *) (cs + 1) + cs->size;
tmp = (struct string *) (endaddr - size) - 1;
tmp->size = size;
cs->size -= size + sizeof(struct string);
cs = tmp;
} else
list_del(&cs->list);
cs->len = len;
INIT_LIST_HEAD(&cs->list);
INIT_LIST_HEAD(&cs->update);
return cs;
}
return NULL;
}
static inline unsigned long
free_string(struct list_head *free_list, struct string *cs)
{
struct string *tmp;
struct list_head *p, *left;
/* Find out the left neighbour in free memory list. */
left = free_list;
list_for_each(p, free_list) {
if (list_entry(p, struct string, list) > cs)
break;
left = p;
}
/* Try to merge with right neighbour = next element from left. */
if (left->next != free_list) {
tmp = list_entry(left->next, struct string, list);
if ((char *) (cs + 1) + cs->size == (char *) tmp) {
list_del(&tmp->list);
cs->size += tmp->size + sizeof(struct string);
}
}
/* Try to merge with left neighbour. */
if (left != free_list) {
tmp = list_entry(left, struct string, list);
if ((char *) (tmp + 1) + tmp->size == (char *) cs) {
tmp->size += cs->size + sizeof(struct string);
return tmp->size;
}
}
__list_add(&cs->list, left, left->next);
return cs->size;
}
static inline void
add_string_memory(struct list_head *free_list, void *mem, unsigned long size)
{
struct string *cs;
cs = (struct string *) mem;
cs->size = size - sizeof(struct string);
free_string(free_list, cs);
}
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