minix/servers/vfs/dmap.c
David van Moolenbroek 723e51327f VFS: worker thread model overhaul
The main purpose of this patch is to fix handling of unpause calls
from PM while another call is ongoing. The solution to this problem
sparked a full revision of the threading model, consisting of a large
number of related changes:

- all active worker threads are now always associated with a process,
  and every process has at most one active thread working for it;
- the process lock is always held by a process's worker thread;
- a process can now have both normal work and postponed PM work
  associated to it;
- timer expiry and non-postponed PM work is done from the main thread;
- filp garbage collection is done from a thread associated with VFS;
- reboot calls from PM are now done from a thread associated with PM;
- the DS events handler is protected from starting multiple threads;
- support for a system worker thread has been removed;
- the deadlock recovery thread has been replaced by a parameter to the
  worker_start() function; the number of worker threads has
  consequently been increased by one;
- saving and restoring of global but per-thread variables is now
  centralized in worker_suspend() and worker_resume(); err_code is now
  saved and restored in all cases;
- the concept of jobs has been removed, and job_m_in now points to a
  message stored in the worker thread structure instead;
- the PM lock has been removed;
- the separate exec lock has been replaced by a lock on the VM
  process, which was already being locked for exec calls anyway;
- PM_UNPAUSE is now processed as a postponed PM request, from a thread
  associated with the target process;
- the FP_DROP_WORK flag has been removed, since it is no longer more
  than just an optimization and only applied to processes operating on
  a pipe when getting killed;
- assignment to "fp" now takes place only when obtaining new work in
  the main thread or a worker thread, when resuming execution of a
  thread, and in the special case of exiting processes during reboot;
- there are no longer special cases where the yield() call is used to
  force a thread to run.

Change-Id: I7a97b9b95c2450454a9b5318dfa0e6150d4e6858
2014-02-18 11:25:03 +01:00

382 lines
11 KiB
C

/* This file contains the table with device <-> driver mappings. It also
* contains some routines to dynamically add and/ or remove device drivers
* or change mappings.
*/
#include "fs.h"
#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <unistd.h>
#include <minix/com.h>
#include <minix/ds.h>
#include "param.h"
/* The order of the entries in the table determines the mapping between major
* device numbers and device drivers. Character and block devices
* can be intermixed at random. The ordering determines the device numbers in
* /dev. Note that the major device numbers used in /dev are NOT the same as
* the process numbers of the device drivers. See <minix/dmap.h> for mappings.
*/
struct dmap dmap[NR_DEVICES];
/*===========================================================================*
* lock_dmap *
*===========================================================================*/
void lock_dmap(struct dmap *dp)
{
/* Lock a driver */
struct worker_thread *org_self;
int r;
assert(dp != NULL);
assert(dp->dmap_driver != NONE);
org_self = worker_suspend();
if ((r = mutex_lock(dp->dmap_lock_ref)) != 0)
panic("unable to get a lock on dmap: %d\n", r);
worker_resume(org_self);
}
/*===========================================================================*
* unlock_dmap *
*===========================================================================*/
void unlock_dmap(struct dmap *dp)
{
/* Unlock a driver */
int r;
assert(dp != NULL);
if ((r = mutex_unlock(dp->dmap_lock_ref)) != 0)
panic("unable to unlock dmap lock: %d\n", r);
}
/*===========================================================================*
* do_mapdriver *
*===========================================================================*/
int do_mapdriver()
{
/* Create a device->driver mapping. RS will tell us which major is driven by
* this driver, what type of device it is (regular, TTY, asynchronous, clone,
* etc), and its label. This label is registered with DS, and allows us to
* retrieve the driver's endpoint.
*/
int r, flags, major, style, slot;
endpoint_t endpoint;
vir_bytes label_vir;
size_t label_len;
char label[LABEL_MAX];
struct fproc *rfp;
/* Only RS can map drivers. */
if (who_e != RS_PROC_NR) return(EPERM);
label_vir = (vir_bytes) job_m_in.md_label;
label_len = (size_t) job_m_in.md_label_len;
major = job_m_in.md_major;
flags = job_m_in.md_flags;
style = job_m_in.md_style;
/* Get the label */
if (label_len+1 > sizeof(label)) { /* Can we store this label? */
printf("VFS: do_mapdriver: label too long\n");
return(EINVAL);
}
r = sys_vircopy(who_e, label_vir, SELF, (vir_bytes) label, label_len);
if (r != OK) {
printf("VFS: do_mapdriver: sys_vircopy failed: %d\n", r);
return(EINVAL);
}
label[label_len] = '\0'; /* Terminate label */
/* Now we know how the driver is called, fetch its endpoint */
r = ds_retrieve_label_endpt(label, &endpoint);
if (r != OK) {
printf("VFS: do_mapdriver: label '%s' unknown\n", label);
return(EINVAL);
}
/* Process is a service */
if (isokendpt(endpoint, &slot) != OK) {
printf("VFS: can't map driver to unknown endpoint %d\n", endpoint);
return(EINVAL);
}
rfp = &fproc[slot];
rfp->fp_flags |= FP_SRV_PROC;
/* Try to update device mapping. */
return map_driver(label, major, endpoint, style, flags);
}
/*===========================================================================*
* map_driver *
*===========================================================================*/
int map_driver(label, major, proc_nr_e, style, flags)
const char label[LABEL_MAX]; /* name of the driver */
int major; /* major number of the device */
endpoint_t proc_nr_e; /* process number of the driver */
int style; /* style of the device */
int flags; /* device flags */
{
/* Add a new device driver mapping in the dmap table. If the proc_nr is set to
* NONE, we're supposed to unmap it.
*/
int slot, s;
size_t len;
struct dmap *dp;
/* Get pointer to device entry in the dmap table. */
if (major < 0 || major >= NR_DEVICES) return(ENODEV);
dp = &dmap[major];
/* Check if we're supposed to unmap it. */
if (proc_nr_e == NONE) {
/* Even when a driver is now unmapped and is shortly to be mapped in
* due to recovery, invalidate associated filps if they're character
* special files. More sophisticated recovery mechanisms which would
* reduce the need to invalidate files are possible, but would require
* cooperation of the driver and more recovery framework between RS,
* VFS, and DS.
*/
invalidate_filp_by_char_major(major);
dp->dmap_opcl = no_dev;
dp->dmap_io = no_dev_io;
dp->dmap_driver = NONE;
dp->dmap_flags = flags;
dp->dmap_lock_ref = &dp->dmap_lock;
return(OK);
}
/* Check process number of new driver if it was alive before mapping */
s = isokendpt(proc_nr_e, &slot);
if (s != OK) {
/* This is not a problem only when we force this driver mapping */
if (! (flags & DRV_FORCED))
return(EINVAL);
}
if (label != NULL) {
len = strlen(label);
if (len+1 > sizeof(dp->dmap_label))
panic("VFS: map_driver: label too long: %d", len);
strlcpy(dp->dmap_label, label, LABEL_MAX);
}
/* Store driver I/O routines based on type of device */
switch (style) {
case STYLE_DEV:
dp->dmap_opcl = gen_opcl;
dp->dmap_io = gen_io;
break;
case STYLE_TTY:
dp->dmap_opcl = tty_opcl;
dp->dmap_io = gen_io;
break;
case STYLE_CTTY:
dp->dmap_opcl = ctty_opcl;
dp->dmap_io = ctty_io;
break;
case STYLE_CLONE:
dp->dmap_opcl = clone_opcl;
dp->dmap_io = gen_io;
break;
default:
return(EINVAL);
}
dp->dmap_driver = proc_nr_e;
dp->dmap_flags = flags;
dp->dmap_style = style;
return(OK);
}
/*===========================================================================*
* dmap_unmap_by_endpt *
*===========================================================================*/
void dmap_unmap_by_endpt(endpoint_t proc_e)
{
/* Lookup driver in dmap table by endpoint and unmap it */
int major, r;
for (major = 0; major < NR_DEVICES; major++) {
if (dmap_driver_match(proc_e, major)) {
/* Found driver; overwrite it with a NULL entry */
if ((r = map_driver(NULL, major, NONE, 0, 0)) != OK) {
printf("VFS: unmapping driver %d for major %d failed:"
" %d\n", proc_e, major, r);
}
}
}
}
/*===========================================================================*
* map_service *
*===========================================================================*/
int map_service(struct rprocpub *rpub)
{
/* Map a new service by storing its device driver properties. */
int r, slot;
struct dmap *fdp, *sdp;
struct fproc *rfp;
if (IS_RPUB_BOOT_USR(rpub)) return(OK);
/* Process is a service */
if (isokendpt(rpub->endpoint, &slot) != OK) {
printf("VFS: can't map service with unknown endpoint %d\n",
rpub->endpoint);
return(EINVAL);
}
rfp = &fproc[slot];
rfp->fp_flags |= FP_SRV_PROC;
/* Not a driver, nothing more to do. */
if (rpub->dev_nr == NO_DEV) return(OK);
/* Map driver. */
r = map_driver(rpub->label, rpub->dev_nr, rpub->endpoint, rpub->dev_style,
rpub->dev_flags);
if(r != OK) return(r);
/* If driver has two major numbers associated, also map the other one. */
if(rpub->dev_style2 != STYLE_NDEV) {
r = map_driver(rpub->label, rpub->dev_nr+1, rpub->endpoint,
rpub->dev_style2, rpub->dev_flags);
if(r != OK) return(r);
/* To ensure that future dmap lock attempts always lock the same driver
* regardless of major number, refer the second dmap lock reference
* to the first dmap entry.
*/
fdp = get_dmap_by_major(rpub->dev_nr);
sdp = get_dmap_by_major(rpub->dev_nr+1);
assert(fdp != NULL);
assert(sdp != NULL);
assert(fdp != sdp);
sdp->dmap_lock_ref = &fdp->dmap_lock;
}
return(OK);
}
/*===========================================================================*
* init_dmap *
*===========================================================================*/
void init_dmap()
{
/* Initialize the table with empty device <-> driver mappings. */
int i;
memset(dmap, 0, sizeof(dmap));
for (i = 0; i < NR_DEVICES; i++) {
dmap[i].dmap_opcl = no_dev;
dmap[i].dmap_io = no_dev_io;
dmap[i].dmap_driver = NONE;
dmap[i].dmap_style = STYLE_NDEV;
dmap[i].dmap_servicing = NONE;
}
}
/*===========================================================================*
* init_dmap_locks *
*===========================================================================*/
void init_dmap_locks()
{
int i;
for (i = 0; i < NR_DEVICES; i++) {
if (mutex_init(&dmap[i].dmap_lock, NULL) != 0)
panic("unable to initialize dmap lock");
dmap[i].dmap_lock_ref = &dmap[i].dmap_lock;
}
}
/*===========================================================================*
* dmap_driver_match *
*===========================================================================*/
int dmap_driver_match(endpoint_t proc, int major)
{
if (major < 0 || major >= NR_DEVICES) return(0);
if (dmap[major].dmap_driver != NONE && dmap[major].dmap_driver == proc)
return(1);
return(0);
}
/*===========================================================================*
* dmap_by_major *
*===========================================================================*/
struct dmap *
get_dmap_by_major(int major)
{
if (major < 0 || major >= NR_DEVICES) return(NULL);
if (dmap[major].dmap_driver == NONE) return(NULL);
return(&dmap[major]);
}
/*===========================================================================*
* dmap_endpt_up *
*===========================================================================*/
void dmap_endpt_up(endpoint_t proc_e, int is_blk)
{
/* A device driver with endpoint proc_e has been restarted. Go tell everyone
* that might be blocking on it that this device is 'up'.
*/
int major;
struct dmap *dp;
struct worker_thread *worker;
if (proc_e == NONE) return;
for (major = 0; major < NR_DEVICES; major++) {
if ((dp = get_dmap_by_major(major)) == NULL) continue;
if (dp->dmap_driver == proc_e) {
if (is_blk) {
if (dp->dmap_recovering) {
printf("VFS: driver recovery failure for"
" major %d\n", major);
if (dp->dmap_servicing != NONE) {
worker = worker_get(dp->dmap_servicing);
worker_stop(worker);
}
dp->dmap_recovering = 0;
continue;
}
dp->dmap_recovering = 1;
bdev_up(major);
dp->dmap_recovering = 0;
} else {
if (dp->dmap_servicing != NONE) {
worker = worker_get(dp->dmap_servicing);
worker_stop(worker);
}
cdev_up(major);
}
}
}
}
/*===========================================================================*
* get_dmap *
*===========================================================================*/
struct dmap *get_dmap(endpoint_t proc_e)
{
/* See if 'proc_e' endpoint belongs to a valid dmap entry. If so, return a
* pointer */
int major;
for (major = 0; major < NR_DEVICES; major++)
if (dmap_driver_match(proc_e, major))
return(&dmap[major]);
return(NULL);
}