/* Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc. Written by Michael I. Bushnell. This file is part of the GNU Hurd. The GNU Hurd is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. The GNU Hurd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ #include "ports.h" #include #include #include #include #include #include #define STACK_SIZE (64 * 1024) #define THREAD_PRI 2 /* XXX To reduce starvation, the priority of new threads is initially depressed. This helps already existing threads complete their job and be recycled to handle new messages. The duration of this depression is made a function of the total number of threads because more threads imply more contention, and the priority of threads blocking on a contended spin lock is also implicitely depressed. Then, if permitted, a greater priority is requested to further decrease the need for additional threads. */ static void adjust_priority (unsigned int totalthreads) { mach_port_t host_priv, self, pset, pset_priv; unsigned int t; error_t err; t = 10 + (((totalthreads - 1) / 100) + 1) * 10; thread_switch (MACH_PORT_NULL, SWITCH_OPTION_DEPRESS, t); err = get_privileged_ports (&host_priv, NULL); if (err) goto error_host_priv; self = mach_thread_self (); err = thread_get_assignment (self, &pset); if (err) goto error_pset; err = host_processor_set_priv (host_priv, pset, &pset_priv); if (err) goto error_pset_priv; err = thread_max_priority (self, pset_priv, 0); if (err) goto error_max_priority; err = thread_priority (self, THREAD_PRI, 0); if (err) goto error_priority; mach_port_deallocate (mach_task_self (), pset_priv); mach_port_deallocate (mach_task_self (), pset); mach_port_deallocate (mach_task_self (), self); mach_port_deallocate (mach_task_self (), host_priv); return; error_priority: error_max_priority: mach_port_deallocate (mach_task_self (), pset_priv); error_pset_priv: mach_port_deallocate (mach_task_self (), pset); error_pset: mach_port_deallocate (mach_task_self (), self); mach_port_deallocate (mach_task_self (), host_priv); error_host_priv: if (err != EPERM) error (0, err, "unable to adjust libports thread priority"); } void ports_manage_port_operations_multithread (struct port_bucket *bucket, ports_demuxer_type demuxer, int thread_timeout, int global_timeout, void (*hook)()) { /* totalthreads is the number of total threads created. nreqthreads is the number of threads not currently servicing any client. The initial values account for the main thread. */ unsigned int totalthreads = 1; unsigned int nreqthreads = 1; pthread_attr_t attr; auto void * thread_function (void *); pthread_attr_init (&attr); pthread_attr_setstacksize (&attr, STACK_SIZE); int internal_demuxer (mach_msg_header_t *inp, mach_msg_header_t *outheadp) { int status; struct port_info *pi; struct rpc_info link; register mig_reply_header_t *outp = (mig_reply_header_t *) outheadp; static const mach_msg_type_t RetCodeType = { /* msgt_name = */ MACH_MSG_TYPE_INTEGER_32, /* msgt_size = */ 32, /* msgt_number = */ 1, /* msgt_inline = */ TRUE, /* msgt_longform = */ FALSE, /* msgt_deallocate = */ FALSE, /* msgt_unused = */ 0 }; if (__atomic_sub_fetch (&nreqthreads, 1, __ATOMIC_RELAXED) == 0) /* No thread would be listening for requests, spawn one. */ { pthread_t pthread_id; error_t err; __atomic_add_fetch (&totalthreads, 1, __ATOMIC_RELAXED); __atomic_add_fetch (&nreqthreads, 1, __ATOMIC_RELAXED); err = pthread_create (&pthread_id, &attr, thread_function, NULL); if (!err) pthread_detach (pthread_id); else { __atomic_sub_fetch (&totalthreads, 1, __ATOMIC_RELAXED); __atomic_sub_fetch (&nreqthreads, 1, __ATOMIC_RELAXED); /* There is not much we can do at this point. The code and design of the Hurd servers just don't handle thread creation failure. */ errno = err; perror ("pthread_create"); } } /* Fill in default response. */ outp->Head.msgh_bits = MACH_MSGH_BITS(MACH_MSGH_BITS_REMOTE(inp->msgh_bits), 0); outp->Head.msgh_size = sizeof *outp; outp->Head.msgh_remote_port = inp->msgh_remote_port; outp->Head.msgh_local_port = MACH_PORT_NULL; outp->Head.msgh_seqno = 0; outp->Head.msgh_id = inp->msgh_id + 100; outp->RetCodeType = RetCodeType; outp->RetCode = MIG_BAD_ID; pi = ports_lookup_port (bucket, inp->msgh_local_port, 0); if (pi) { error_t err = ports_begin_rpc (pi, inp->msgh_id, &link); if (err) { outp->RetCode = err; status = 1; } else { pthread_mutex_lock (&_ports_lock); if (inp->msgh_seqno < pi->cancel_threshold) hurd_thread_cancel (link.thread); pthread_mutex_unlock (&_ports_lock); status = demuxer (inp, outheadp); ports_end_rpc (pi, &link); } ports_port_deref (pi); } else { outp->RetCode = EOPNOTSUPP; status = 1; } __atomic_add_fetch (&nreqthreads, 1, __ATOMIC_RELAXED); return status; } void * thread_function (void *arg) { int master = (int) arg; int timeout; error_t err; adjust_priority (__atomic_load_n (&totalthreads, __ATOMIC_RELAXED)); if (hook) (*hook) (); if (master) timeout = global_timeout; else timeout = thread_timeout; startover: do err = mach_msg_server_timeout (internal_demuxer, 0, bucket->portset, timeout ? MACH_RCV_TIMEOUT : 0, timeout); while (err != MACH_RCV_TIMED_OUT); if (master) { if (__atomic_load_n (&totalthreads, __ATOMIC_RELAXED) != 1) goto startover; } else { if (__atomic_sub_fetch (&nreqthreads, 1, __ATOMIC_RELAXED) == 0) { /* No other thread is listening for requests, continue. */ __atomic_add_fetch (&nreqthreads, 1, __ATOMIC_RELAXED); goto startover; } __atomic_sub_fetch (&totalthreads, 1, __ATOMIC_RELAXED); } return NULL; } /* XXX It is currently unsafe for most servers to terminate based on inactivity because a request may arrive after a server has started shutting down, causing the client to receive an error. Prevent the master thread from going away. */ global_timeout = 0; thread_function ((void *) 1); }