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minix/servers/vfs/pipe.c

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/* This file deals with the suspension and revival of processes. A process can
* be suspended because it wants to read or write from a pipe and can't, or
* because it wants to read or write from a special file and can't. When a
* process can't continue it is suspended, and revived later when it is able
* to continue.
*
* The entry points into this file are
* do_pipe: perform the PIPE system call
* pipe_check: check to see that a read or write on a pipe is feasible now
* suspend: suspend a process that cannot do a requested read or write
* release: check to see if a suspended process can be released and do
* it
* revive: mark a suspended process as able to run again
* unsuspend_by_endpt: revive all processes blocking on a given process
* do_unpause: a signal has been sent to a process; see if it suspended
*/
#include "fs.h"
#include <fcntl.h>
#include <signal.h>
#include <assert.h>
#include <minix/callnr.h>
#include <minix/endpoint.h>
#include <minix/com.h>
#include <minix/u64.h>
#include <sys/select.h>
#include <sys/time.h>
#include "file.h"
#include "fproc.h"
#include "param.h"
#include "select.h"
#include <minix/vfsif.h>
#include "vnode.h"
#include "vmnt.h"
/*===========================================================================*
* do_pipe *
*===========================================================================*/
PUBLIC int do_pipe()
{
/* Perform the pipe(fil_des) system call. */
register struct fproc *rfp;
int r;
struct filp *fil_ptr0, *fil_ptr1;
int fil_des[2]; /* reply goes here */
struct vnode *vp;
struct node_details res;
/* See if a free vnode is available */
if ( (vp = get_free_vnode()) == NULL) return(err_code);
/* Acquire two file descriptors. */
rfp = fp;
if ((r = get_fd(0, R_BIT, &fil_des[0], &fil_ptr0)) != OK) return(r);
rfp->fp_filp[fil_des[0]] = fil_ptr0;
FD_SET(fil_des[0], &rfp->fp_filp_inuse);
fil_ptr0->filp_count = 1;
if ((r = get_fd(0, W_BIT, &fil_des[1], &fil_ptr1)) != OK) {
rfp->fp_filp[fil_des[0]] = NULL;
FD_CLR(fil_des[0], &rfp->fp_filp_inuse);
fil_ptr0->filp_count = 0;
return(r);
}
rfp->fp_filp[fil_des[1]] = fil_ptr1;
FD_SET(fil_des[1], &rfp->fp_filp_inuse);
fil_ptr1->filp_count = 1;
/* Create a named pipe inode on PipeFS */
r = req_newnode(PFS_PROC_NR, fp->fp_effuid, fp->fp_effgid, I_NAMED_PIPE,
NO_DEV, &res);
if (r != OK) {
rfp->fp_filp[fil_des[0]] = NULL;
FD_CLR(fil_des[0], &rfp->fp_filp_inuse);
fil_ptr0->filp_count = 0;
rfp->fp_filp[fil_des[1]] = NULL;
FD_CLR(fil_des[1], &rfp->fp_filp_inuse);
fil_ptr1->filp_count = 0;
return(r);
}
/* Fill in vnode */
vp->v_fs_e = res.fs_e;
vp->v_mapfs_e = res.fs_e;
vp->v_inode_nr = res.inode_nr;
vp->v_mapinode_nr = res.inode_nr;
vp->v_mode = res.fmode;
vp->v_pipe = I_PIPE;
vp->v_pipe_rd_pos= 0;
vp->v_pipe_wr_pos= 0;
vp->v_fs_count = 1;
vp->v_mapfs_count = 1;
vp->v_ref_count = 1;
vp->v_size = 0;
vp->v_vmnt = NULL;
vp->v_dev = NO_DEV;
/* Fill in filp objects */
fil_ptr0->filp_vno = vp;
dup_vnode(vp);
fil_ptr1->filp_vno = vp;
fil_ptr0->filp_flags = O_RDONLY;
fil_ptr1->filp_flags = O_WRONLY;
m_out.reply_i1 = fil_des[0];
m_out.reply_i2 = fil_des[1];
return(OK);
}
/*===========================================================================*
* map_vnode *
*===========================================================================*/
PUBLIC int map_vnode(vp)
struct vnode *vp;
{
int r;
struct node_details res;
if(vp->v_mapfs_e != 0) return(OK); /* Already mapped; nothing to do. */
/* Create a temporary mapping of this inode to PipeFS. Read and write
* operations on data will be handled by PipeFS. The rest by the 'original'
* FS that holds the inode. */
if ((r = req_newnode(PFS_PROC_NR, fp->fp_effuid, fp->fp_effgid, I_NAMED_PIPE,
vp->v_dev, &res)) == OK) {
vp->v_mapfs_e = res.fs_e;
vp->v_mapinode_nr = res.inode_nr;
vp->v_mapfs_count = 1;
}
return(r);
}
/*===========================================================================*
* pipe_check *
*===========================================================================*/
PUBLIC int pipe_check(vp, rw_flag, oflags, bytes, position, notouch)
register struct vnode *vp; /* the inode of the pipe */
int rw_flag; /* READING or WRITING */
int oflags; /* flags set by open or fcntl */
register int bytes; /* bytes to be read or written (all chunks) */
u64_t position; /* current file position */
int notouch; /* check only */
{
/* Pipes are a little different. If a process reads from an empty pipe for
* which a writer still exists, suspend the reader. If the pipe is empty
* and there is no writer, return 0 bytes. If a process is writing to a
* pipe and no one is reading from it, give a broken pipe error.
*/
off_t pos;
int r = OK;
if (ex64hi(position) != 0)
panic("pipe_check: position too large in pipe");
pos = ex64lo(position);
/* If reading, check for empty pipe. */
if (rw_flag == READING) {
if (pos >= vp->v_size) {
/* Process is reading from an empty pipe. */
if (find_filp(vp, W_BIT) != NULL) {
/* Writer exists */
if (oflags & O_NONBLOCK)
r = EAGAIN;
else
r = SUSPEND;
/* If need be, activate sleeping writers. */
if (susp_count > 0)
release(vp, WRITE, susp_count);
}
return(r);
}
return(bytes);
}
/* Process is writing to a pipe. */
if (find_filp(vp, R_BIT) == NULL) {
/* Process is writing, but there is no reader. Tell kernel to generate
* a SIGPIPE signal. */
if (!notouch) sys_kill(fp->fp_endpoint, SIGPIPE);
return(EPIPE);
}
/* Calculate how many bytes can be written. */
if (pos + bytes > PIPE_BUF) {
if (oflags & O_NONBLOCK) {
if (bytes <= PIPE_BUF) {
/* Write has to be atomic */
return(EAGAIN);
}
/* Compute available space */
bytes = PIPE_BUF - pos;
if (bytes > 0) {
/* Do a partial write. Need to wakeup reader */
if (!notouch)
release(vp, READ, susp_count);
return(bytes);
} else {
/* Pipe is full */
return(EAGAIN);
}
}
if (bytes > PIPE_BUF) {
/* Compute available space */
bytes = PIPE_BUF - pos;
if (bytes > 0) {
/* Do a partial write. Need to wakeup reader
* since we'll suspend ourself in read_write()
*/
if (!notouch)
release(vp, READ, susp_count);
return(bytes);
}
}
/* Pipe is full */
return(SUSPEND);
}
/* Writing to an empty pipe. Search for suspended reader. */
if (pos == 0 && !notouch)
release(vp, READ, susp_count);
/* Requested amount fits */
return(bytes);
}
/*===========================================================================*
* suspend *
*===========================================================================*/
PUBLIC void suspend(int why)
{
/* Take measures to suspend the processing of the present system call.
* Store the parameters to be used upon resuming in the process table.
* (Actually they are not used when a process is waiting for an I/O device,
* but they are needed for pipes, and it is not worth making the distinction.)
* The SUSPEND pseudo error should be returned after calling suspend().
*/
#if DO_SANITYCHECKS
if (why == FP_BLOCKED_ON_PIPE)
panic("suspend: called for FP_BLOCKED_ON_PIPE");
if(fp_is_blocked(fp))
panic("suspend: called for suspended process");
if(why == FP_BLOCKED_ON_NONE)
panic("suspend: called for FP_BLOCKED_ON_NONE");
#endif
if (why == FP_BLOCKED_ON_POPEN)
/* #procs susp'ed on pipe*/
susp_count++;
fp->fp_blocked_on = why;
assert(fp->fp_grant == GRANT_INVALID || !GRANT_VALID(fp->fp_grant));
fp->fp_block_fd = m_in.fd;
fp->fp_block_callnr = call_nr;
fp->fp_flags &= ~SUSP_REOPEN; /* Clear this flag. The caller
* can set it when needed.
*/
if (why == FP_BLOCKED_ON_LOCK) {
fp->fp_buffer = (char *) m_in.name1; /* third arg to fcntl() */
fp->fp_nbytes = m_in.request; /* second arg to fcntl() */
} else {
fp->fp_buffer = m_in.buffer; /* for reads and writes */
fp->fp_nbytes = m_in.nbytes;
}
}
/*===========================================================================*
* wait_for *
*===========================================================================*/
PUBLIC void wait_for(endpoint_t who)
{
if(who == NONE || who == ANY)
panic("suspend on NONE or ANY");
suspend(FP_BLOCKED_ON_OTHER);
fp->fp_task = who;
}
/*===========================================================================*
* pipe_suspend *
*===========================================================================*/
PUBLIC void pipe_suspend(rw_flag, fd_nr, buf, size)
int rw_flag;
int fd_nr;
char *buf;
size_t size;
{
/* Take measures to suspend the processing of the present system call.
* Store the parameters to be used upon resuming in the process table.
* (Actually they are not used when a process is waiting for an I/O device,
* but they are needed for pipes, and it is not worth making the distinction.)
* The SUSPEND pseudo error should be returned after calling suspend().
*/
#if DO_SANITYCHECKS
if(fp_is_blocked(fp))
panic("pipe_suspend: called for suspended process");
#endif
susp_count++; /* #procs susp'ed on pipe*/
fp->fp_blocked_on = FP_BLOCKED_ON_PIPE;
assert(!GRANT_VALID(fp->fp_grant));
fp->fp_block_fd = fd_nr;
fp->fp_block_callnr = ((rw_flag == READING) ? READ : WRITE);
fp->fp_buffer = buf;
fp->fp_nbytes = size;
}
/*===========================================================================*
* unsuspend_by_endpt *
*===========================================================================*/
PUBLIC void unsuspend_by_endpt(endpoint_t proc_e)
{
struct fproc *rp;
/* Revive processes waiting for drivers (SUSPENDed) that have
* disappeared with return code EAGAIN.
*/
for (rp = &fproc[0]; rp < &fproc[NR_PROCS]; rp++)
if(rp->fp_pid != PID_FREE &&
rp->fp_blocked_on == FP_BLOCKED_ON_OTHER && rp->fp_task == proc_e) {
revive(rp->fp_endpoint, EAGAIN);
}
/* Revive processes waiting in drivers on select()s
* with EAGAIN too.
*/
select_unsuspend_by_endpt(proc_e);
return;
}
/*===========================================================================*
* release *
*===========================================================================*/
PUBLIC void release(vp, call_nr, count)
register struct vnode *vp; /* inode of pipe */
int call_nr; /* READ, WRITE, OPEN or CREAT */
int count; /* max number of processes to release */
{
/* Check to see if any process is hanging on the pipe whose inode is in 'ip'.
* If one is, and it was trying to perform the call indicated by 'call_nr',
* release it.
*/
register struct fproc *rp;
struct filp *f;
/* Trying to perform the call also includes SELECTing on it with that
* operation.
*/
if (call_nr == READ || call_nr == WRITE) {
int op;
if (call_nr == READ)
op = SEL_RD;
else
op = SEL_WR;
for(f = &filp[0]; f < &filp[NR_FILPS]; f++) {
if (f->filp_count < 1 || !(f->filp_pipe_select_ops & op) ||
f->filp_vno != vp)
continue;
select_callback(f, op);
f->filp_pipe_select_ops &= ~op;
}
}
/* Search the proc table. */
for (rp = &fproc[0]; rp < &fproc[NR_PROCS] && count > 0; rp++) {
if (rp->fp_pid != PID_FREE && fp_is_blocked(rp) &&
rp->fp_revived == NOT_REVIVING && rp->fp_block_callnr == call_nr &&
rp->fp_filp[rp->fp_block_fd]->filp_vno == vp) {
revive(rp->fp_endpoint, 0);
susp_count--; /* keep track of who is suspended */
if(susp_count < 0)
panic("susp_count now negative: %d", susp_count);
if (--count == 0) return;
}
}
}
/*===========================================================================*
* revive *
*===========================================================================*/
PUBLIC void revive(proc_nr_e, returned)
int proc_nr_e; /* process to revive */
int returned; /* if hanging on task, how many bytes read */
{
/* Revive a previously blocked process. When a process hangs on tty, this
* is the way it is eventually released.
*/
register struct fproc *rfp;
int blocked_on;
int fd_nr, proc_nr;
struct filp *fil_ptr;
if(isokendpt(proc_nr_e, &proc_nr) != OK) return;
rfp = &fproc[proc_nr];
if (!fp_is_blocked(rfp) || rfp->fp_revived == REVIVING) return;
/* The 'reviving' flag only applies to pipes. Processes waiting for TTY get
* a message right away. The revival process is different for TTY and pipes.
* For select and TTY revival, the work is already done, for pipes it is not:
* the proc must be restarted so it can try again.
*/
blocked_on = rfp->fp_blocked_on;
if (blocked_on == FP_BLOCKED_ON_PIPE || blocked_on == FP_BLOCKED_ON_LOCK) {
/* Revive a process suspended on a pipe or lock. */
rfp->fp_revived = REVIVING;
reviving++; /* process was waiting on pipe or lock */
} else if (blocked_on == FP_BLOCKED_ON_DOPEN) {
rfp->fp_blocked_on = FP_BLOCKED_ON_NONE;
fd_nr = rfp->fp_block_fd;
if (returned < 0) {
fil_ptr = rfp->fp_filp[fd_nr];
rfp->fp_filp[fd_nr] = NULL;
FD_CLR(fd_nr, &rfp->fp_filp_inuse);
if (fil_ptr->filp_count != 1) {
panic("revive: bad count in filp: %d",
fil_ptr->filp_count);
}
fil_ptr->filp_count = 0;
put_vnode(fil_ptr->filp_vno);
fil_ptr->filp_vno = NULL;
reply(proc_nr_e, returned);
} else
reply(proc_nr_e, fd_nr);
} else {
rfp->fp_blocked_on = FP_BLOCKED_ON_NONE;
if (blocked_on == FP_BLOCKED_ON_POPEN) {
/* process blocked in open or create */
reply(proc_nr_e, rfp->fp_block_fd);
} else if (blocked_on == FP_BLOCKED_ON_SELECT) {
reply(proc_nr_e, returned);
} else {
/* Revive a process suspended on TTY or other device.
* Pretend it wants only what there is.
*/
rfp->fp_nbytes = returned;
/* If a grant has been issued by FS for this I/O, revoke
* it again now that I/O is done.
*/
if(GRANT_VALID(rfp->fp_grant)) {
if(cpf_revoke(rfp->fp_grant)) {
panic("FS: revoke failed for grant: %d",
rfp->fp_grant);
}
rfp->fp_grant = GRANT_INVALID;
}
reply(proc_nr_e, returned); /* unblock the process */
}
}
}
/*===========================================================================*
* unpause *
*===========================================================================*/
PUBLIC void unpause(proc_nr_e)
int proc_nr_e;
{
/* A signal has been sent to a user who is paused on the file system.
* Abort the system call with the EINTR error message.
*/
register struct fproc *rfp;
int proc_nr_p, blocked_on, fild, status = EINTR;
struct filp *f;
dev_t dev;
message mess;
int wasreviving = 0;
if(isokendpt(proc_nr_e, &proc_nr_p) != OK) {
printf("VFS: ignoring unpause for bogus endpoint %d\n", proc_nr_e);
return;
}
rfp = &fproc[proc_nr_p];
if (!fp_is_blocked(rfp)) return;
blocked_on = rfp->fp_blocked_on;
if (rfp->fp_revived == REVIVING) {
rfp->fp_revived = NOT_REVIVING;
reviving--;
wasreviving = 1;
}
switch (blocked_on) {
case FP_BLOCKED_ON_PIPE:/* process trying to read or write a pipe */
break;
case FP_BLOCKED_ON_LOCK:/* process trying to set a lock with FCNTL */
break;
case FP_BLOCKED_ON_SELECT:/* process blocking on select() */
select_forget(proc_nr_e);
break;
case FP_BLOCKED_ON_POPEN: /* process trying to open a fifo */
break;
case FP_BLOCKED_ON_DOPEN:/* process trying to open a device */
/* Don't cancel OPEN. Just wait until the open completes. */
return;
case FP_BLOCKED_ON_OTHER: /* process trying to do device I/O (e.g. tty)*/
if (rfp->fp_flags & SUSP_REOPEN) {
/* Process is suspended while waiting for a reopen.
* Just reply EINTR.
*/
rfp->fp_flags &= ~SUSP_REOPEN;
status = EINTR;
break;
}
fild = rfp->fp_block_fd;
if (fild < 0 || fild >= OPEN_MAX)
panic("unpause err 2");
f = rfp->fp_filp[fild];
dev = (dev_t) f->filp_vno->v_sdev; /* device hung on */
mess.TTY_LINE = (dev >> MINOR) & BYTE;
mess.IO_ENDPT = rfp->fp_ioproc;
mess.IO_GRANT = (char *) rfp->fp_grant;
/* Tell kernel R or W. Mode is from current call, not open. */
mess.COUNT = rfp->fp_block_callnr == READ ? R_BIT : W_BIT;
mess.m_type = CANCEL;
fp = rfp; /* hack - ctty_io uses fp */
(*dmap[(dev >> MAJOR) & BYTE].dmap_io)(rfp->fp_task, &mess);
status = mess.REP_STATUS;
if (status == SUSPEND)
return; /* Process will be revived at a
* later time.
*/
if(status == EAGAIN) status = EINTR;
if(GRANT_VALID(rfp->fp_grant)) {
if(cpf_revoke(rfp->fp_grant)) {
panic("FS: revoke failed for grant (cancel): %d",
rfp->fp_grant);
}
rfp->fp_grant = GRANT_INVALID;
}
break;
default :
panic("FS: unknown value: %d", blocked_on);
}
rfp->fp_blocked_on = FP_BLOCKED_ON_NONE;
if ((blocked_on == FP_BLOCKED_ON_PIPE ||
blocked_on == FP_BLOCKED_ON_POPEN) &&
!wasreviving) {
susp_count--;
}
reply(proc_nr_e, status); /* signal interrupted call */
}
/*===========================================================================*
* select_request_pipe *
*===========================================================================*/
PUBLIC int select_request_pipe(struct filp *f, int *ops, int block)
{
int orig_ops, r = 0, err;
orig_ops = *ops;
if ((*ops & (SEL_RD|SEL_ERR))) {
if ((err = pipe_check(f->filp_vno, READING, 0,
1, f->filp_pos, 1)) != SUSPEND)
r |= SEL_RD;
if (err < 0 && err != SUSPEND)
r |= SEL_ERR;
if(err == SUSPEND && f->filp_mode & W_BIT) {
/* A "meaningless" read select, therefore ready
for reading and no error set. */
r |= SEL_RD;
r &= ~SEL_ERR;
}
}
if ((*ops & (SEL_WR|SEL_ERR))) {
if ((err = pipe_check(f->filp_vno, WRITING, 0,
1, f->filp_pos, 1)) != SUSPEND)
r |= SEL_WR;
if (err < 0 && err != SUSPEND)
r |= SEL_ERR;
if(err == SUSPEND && f->filp_mode & R_BIT) {
/* A "meaningless" write select, therefore ready
for reading and no error set. */
r |= SEL_WR;
r &= ~SEL_ERR;
}
}
/* Some options we collected might not be requested. */
*ops = r & orig_ops;
if (!*ops && block) {
f->filp_pipe_select_ops |= orig_ops;
}
return(SEL_OK);
}
/*===========================================================================*
* select_match_pipe *
*===========================================================================*/
PUBLIC int select_match_pipe(struct filp *f)
{
/* recognize either pipe or named pipe (FIFO) */
if (f && f->filp_vno && (f->filp_vno->v_mode & I_NAMED_PIPE))
return 1;
return 0;
}
#if DO_SANITYCHECKS
/*===========================================================================*
* check_pipe *
*===========================================================================*/
PUBLIC int check_pipe(void)
{
struct fproc *rfp;
int mycount = 0;
for (rfp=&fproc[0]; rfp < &fproc[NR_PROCS]; rfp++) {
if (rfp->fp_pid == PID_FREE)
continue;
if(rfp->fp_revived != REVIVING &&
(rfp->fp_blocked_on == FP_BLOCKED_ON_PIPE ||
rfp->fp_blocked_on == FP_BLOCKED_ON_POPEN)) {
mycount++;
}
}
if(mycount != susp_count) {
printf("check_pipe: mycount %d susp_count %d\n",
mycount, susp_count);
return 0;
}
return 1;
}
#endif
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