diff options
Diffstat (limited to 'trans')
| -rw-r--r-- | trans/fifo.c | 75 |
1 files changed, 52 insertions, 23 deletions
diff --git a/trans/fifo.c b/trans/fifo.c index 129508e5..08d20198 100644 --- a/trans/fifo.c +++ b/trans/fifo.c @@ -34,7 +34,7 @@ #include <hurd/pipe.h> /* Global options. These defaults are the standard ones, I think... */ -int wait_for_reader = 1; +int wait_for_reader = 1, wait_for_writer = 1; int one_reader = 1; /* What kinds of pipes we use. */ @@ -64,7 +64,7 @@ usage(int status) printf("\ \n\ -r, --multiple-readers Allow multiple simultaneous readers\n\ - -n, --noblock Don't block on open if there are no readers\n\ + -n, --noblock Don't block on open\n\ -d, --dgram Reads reflect write record boundaries\n\ --help Give this usage message\n\ "); @@ -106,7 +106,7 @@ main (int argc, char **argv) switch (opt) { case 'r': one_reader = 0; break; - case 'n': wait_for_reader = 0; break; + case 'n': wait_for_reader = wait_for_writer = 0; break; case 'd': fifo_pipe_class = seqpack_pipe_class; case '&': usage(0); default: usage(1); @@ -158,22 +158,28 @@ open_hook (struct trivfs_peropen *po) error_t err = 0; int flags = po->openmodes; +/* Wait until the active fifo has changed so that CONDITION is true. */ +#define WAIT(condition) \ + while (!err && !(condition)) \ + if (flags & O_NONBLOCK) \ + err = EWOULDBLOCK; \ + else if (hurd_condition_wait (&active_fifo_changed, &active_fifo_lock)) \ + err = EINTR; + mutex_lock (&active_fifo_lock); if (flags & O_READ) /* When opening for read, what we do depends on what mode this server is running in. The default (if ONE_READER is set) is to only allow one reader at a time, with additional opens for read blocking here until - the old reader goes away; otherwise, we allow multiple readers. */ + the old reader goes away; otherwise, we allow multiple readers. If + WAIT_FOR_WRITER is true, then once we've created a fifo, we also block + until someone opens it for writing; otherwise, the first read will + block until someone writes something. */ { if (one_reader) /* Wait until there isn't any active fifo, so we can make one. */ - while (!err && (active_fifo != NULL || active_fifo->readers > 0)) - if (flags & O_NONBLOCK) - err = EWOULDBLOCK; - else if (hurd_condition_wait (&active_fifo_changed, - &active_fifo_lock)) - err = EINTR; + WAIT (!active_fifo || !active_fifo->readers); if (!err && active_fifo == NULL) /* No other readers, and indeed, no fifo; make one. */ @@ -184,6 +190,22 @@ open_hook (struct trivfs_peropen *po) condition_broadcast (&active_fifo_changed); /* We'll unlock ACTIVE_FIFO_LOCK below; the writer code won't make us block because we've ensured that there's a reader for it. */ + + if (wait_for_writer) + /* Wait until there's a writer. */ + { + WAIT (active_fifo->writers); + if (err) + /* Back out the new pipe creation. */ + { + pipe_remove_reader (active_fifo); + active_fifo = NULL; + condition_broadcast (&active_fifo_changed); + } + } + else + /* Otherwise prevent an immediate eof. */ + active_fifo->flags &= ~PIPE_BROKEN; } } @@ -195,18 +217,19 @@ open_hook (struct trivfs_peropen *po) { if (wait_for_reader) /* Wait until there's a fifo to write to. */ - while (!err && (active_fifo == NULL || active_fifo->readers == 0)) - if (flags & O_NONBLOCK) - err = EWOULDBLOCK; - else if (hurd_condition_wait (&active_fifo_changed, - &active_fifo_lock)) - err = EINTR; - + WAIT (active_fifo && active_fifo->readers); if (!err && active_fifo == NULL) /* No other readers, and indeed, no fifo; make one. */ - err = pipe_create (fifo_pipe_class, &active_fifo); + { + err = pipe_create (fifo_pipe_class, &active_fifo); + if (!err) + active_fifo->flags &= ~PIPE_BROKEN; + } if (!err) - pipe_add_writer (active_fifo); + { + pipe_add_writer (active_fifo); + condition_broadcast (&active_fifo_changed); + } } po->hook = active_fifo; @@ -223,6 +246,9 @@ close_hook (struct trivfs_peropen *po) int flags = po->openmodes; struct pipe *pipe = po->hook; + if (!pipe) + return; + mutex_lock (&active_fifo_lock); was_active = (active_fifo == pipe); @@ -272,10 +298,13 @@ trivfs_modify_stat (struct trivfs_protid *cred, struct stat *st) st->st_mode &= ~S_IFMT; st->st_mode |= S_IFIFO; - mutex_lock (&pipe->lock); - st->st_size = pipe_readable (pipe, 1); - st->st_blocks = st->st_size >> 9; - mutex_unlock (&pipe->lock); + if (pipe) + { + mutex_lock (&pipe->lock); + st->st_size = pipe_readable (pipe, 1); + st->st_blocks = st->st_size >> 9; + mutex_unlock (&pipe->lock); + } /* As we try to be clever with large transfers, ask for them. */ st->st_blksize = vm_page_size * 16; |