1bc93bb7b9
limits in the code which is deep in the call stack, and owns several critical system resources, like vnode locks. Attempt to wait while the per-mount softupdate thread cleans up the backlog may deadlock, because the thread might need to lock the same vnode which is owned by the waiting thread. Instead of synchronously waiting for the worker, perform the worker' tickle and pause until the backlog is cleaned, at the safe point during return from kernel to usermode. A new ast request to call softdep_ast_cleanup() is created, the SU code now only checks the size of queue and schedules ast. There is no ast delivery for the kernel threads, so they are exempted from the mechanism, except NFS daemon threads. NFS server loop explicitely checks for the request, and informs the schedule_cleanup() that it is capable of handling the requests by the process P2_AST_SU flag. This is needed because nfsd may be the sole cause of the SU workqueue overflow. But, to not cause nsfd to spawn additional threads just because we slow down existing workers, only tickle su threads, without waiting for the backlog cleanup. Reviewed by: jhb, mckusick Tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 2 weeks
307 lines
8.8 KiB
C
307 lines
8.8 KiB
C
/*-
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* Copyright (C) 1994, David Greenman
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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* Copyright (c) 2007 The FreeBSD Foundation
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*
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* This code is derived from software contributed to Berkeley by
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* the University of Utah, and William Jolitz.
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*
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* Portions of this software were developed by A. Joseph Koshy under
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* sponsorship from the FreeBSD Foundation and Google, Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: @(#)trap.c 7.4 (Berkeley) 5/13/91
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_hwpmc_hooks.h"
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#include "opt_ktrace.h"
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#include "opt_sched.h"
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#include <sys/param.h>
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#include <sys/bus.h>
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#include <sys/capsicum.h>
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#include <sys/kernel.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/pmckern.h>
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#include <sys/proc.h>
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#include <sys/ktr.h>
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#include <sys/pioctl.h>
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#include <sys/ptrace.h>
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#include <sys/racct.h>
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#include <sys/resourcevar.h>
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#include <sys/sched.h>
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#include <sys/signalvar.h>
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#include <sys/syscall.h>
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#include <sys/syscallsubr.h>
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#include <sys/sysent.h>
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#include <sys/systm.h>
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#include <sys/vmmeter.h>
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#ifdef KTRACE
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#include <sys/uio.h>
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#include <sys/ktrace.h>
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#endif
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#include <security/audit/audit.h>
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#include <machine/cpu.h>
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#ifdef VIMAGE
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#include <net/vnet.h>
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#endif
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#ifdef HWPMC_HOOKS
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#include <sys/pmckern.h>
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#endif
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#include <security/mac/mac_framework.h>
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void (*softdep_ast_cleanup)(void);
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/*
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* Define the code needed before returning to user mode, for trap and
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* syscall.
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*/
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void
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userret(struct thread *td, struct trapframe *frame)
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{
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struct proc *p = td->td_proc;
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CTR3(KTR_SYSC, "userret: thread %p (pid %d, %s)", td, p->p_pid,
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td->td_name);
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KASSERT((p->p_flag & P_WEXIT) == 0,
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("Exiting process returns to usermode"));
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#if 0
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#ifdef DIAGNOSTIC
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/* Check that we called signotify() enough. */
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PROC_LOCK(p);
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thread_lock(td);
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if (SIGPENDING(td) && ((td->td_flags & TDF_NEEDSIGCHK) == 0 ||
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(td->td_flags & TDF_ASTPENDING) == 0))
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printf("failed to set signal flags properly for ast()\n");
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thread_unlock(td);
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PROC_UNLOCK(p);
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#endif
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#endif
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#ifdef KTRACE
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KTRUSERRET(td);
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#endif
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if (softdep_ast_cleanup != NULL)
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softdep_ast_cleanup();
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/*
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* If this thread tickled GEOM, we need to wait for the giggling to
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* stop before we return to userland
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*/
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if (td->td_pflags & TDP_GEOM)
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g_waitidle();
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/*
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* Charge system time if profiling.
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*/
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if (p->p_flag & P_PROFIL)
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addupc_task(td, TRAPF_PC(frame), td->td_pticks * psratio);
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/*
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* Let the scheduler adjust our priority etc.
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*/
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sched_userret(td);
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/*
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* Check for misbehavior.
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*
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* In case there is a callchain tracing ongoing because of
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* hwpmc(4), skip the scheduler pinning check.
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* hwpmc(4) subsystem, infact, will collect callchain informations
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* at ast() checkpoint, which is past userret().
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*/
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WITNESS_WARN(WARN_PANIC, NULL, "userret: returning");
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KASSERT(td->td_critnest == 0,
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("userret: Returning in a critical section"));
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KASSERT(td->td_locks == 0,
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("userret: Returning with %d locks held", td->td_locks));
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KASSERT(td->td_rw_rlocks == 0,
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("userret: Returning with %d rwlocks held in read mode",
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td->td_rw_rlocks));
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KASSERT((td->td_pflags & TDP_NOFAULTING) == 0,
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("userret: Returning with pagefaults disabled"));
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KASSERT(td->td_no_sleeping == 0,
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("userret: Returning with sleep disabled"));
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KASSERT(td->td_pinned == 0 || (td->td_pflags & TDP_CALLCHAIN) != 0,
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("userret: Returning with with pinned thread"));
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KASSERT(td->td_vp_reserv == 0,
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("userret: Returning while holding vnode reservation"));
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KASSERT((td->td_flags & TDF_SBDRY) == 0,
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("userret: Returning with stop signals deferred"));
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KASSERT(td->td_su == NULL,
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("userret: Returning with SU cleanup request not handled"));
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#ifdef VIMAGE
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/* Unfortunately td_vnet_lpush needs VNET_DEBUG. */
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VNET_ASSERT(curvnet == NULL,
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("%s: Returning on td %p (pid %d, %s) with vnet %p set in %s",
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__func__, td, p->p_pid, td->td_name, curvnet,
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(td->td_vnet_lpush != NULL) ? td->td_vnet_lpush : "N/A"));
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#endif
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#ifdef RACCT
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if (racct_enable) {
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PROC_LOCK(p);
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while (p->p_throttled == 1)
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msleep(p->p_racct, &p->p_mtx, 0, "racct", 0);
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PROC_UNLOCK(p);
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}
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#endif
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}
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/*
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* Process an asynchronous software trap.
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* This is relatively easy.
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* This function will return with preemption disabled.
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*/
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void
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ast(struct trapframe *framep)
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{
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struct thread *td;
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struct proc *p;
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int flags;
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int sig;
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td = curthread;
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p = td->td_proc;
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CTR3(KTR_SYSC, "ast: thread %p (pid %d, %s)", td, p->p_pid,
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p->p_comm);
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KASSERT(TRAPF_USERMODE(framep), ("ast in kernel mode"));
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WITNESS_WARN(WARN_PANIC, NULL, "Returning to user mode");
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mtx_assert(&Giant, MA_NOTOWNED);
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THREAD_LOCK_ASSERT(td, MA_NOTOWNED);
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td->td_frame = framep;
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td->td_pticks = 0;
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/*
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* This updates the td_flag's for the checks below in one
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* "atomic" operation with turning off the astpending flag.
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* If another AST is triggered while we are handling the
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* AST's saved in flags, the astpending flag will be set and
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* ast() will be called again.
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*/
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thread_lock(td);
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flags = td->td_flags;
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td->td_flags &= ~(TDF_ASTPENDING | TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK |
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TDF_NEEDRESCHED | TDF_ALRMPEND | TDF_PROFPEND | TDF_MACPEND);
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thread_unlock(td);
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PCPU_INC(cnt.v_trap);
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if (td->td_ucred != p->p_ucred)
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cred_update_thread(td);
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if (td->td_pflags & TDP_OWEUPC && p->p_flag & P_PROFIL) {
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addupc_task(td, td->td_profil_addr, td->td_profil_ticks);
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td->td_profil_ticks = 0;
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td->td_pflags &= ~TDP_OWEUPC;
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}
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#ifdef HWPMC_HOOKS
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/* Handle Software PMC callchain capture. */
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if (PMC_IS_PENDING_CALLCHAIN(td))
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PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_USER_CALLCHAIN_SOFT, (void *) framep);
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#endif
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if (flags & TDF_ALRMPEND) {
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PROC_LOCK(p);
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kern_psignal(p, SIGVTALRM);
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PROC_UNLOCK(p);
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}
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if (flags & TDF_PROFPEND) {
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PROC_LOCK(p);
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kern_psignal(p, SIGPROF);
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PROC_UNLOCK(p);
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}
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#ifdef MAC
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if (flags & TDF_MACPEND)
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mac_thread_userret(td);
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#endif
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if (flags & TDF_NEEDRESCHED) {
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW))
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ktrcsw(1, 1, __func__);
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#endif
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thread_lock(td);
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sched_prio(td, td->td_user_pri);
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mi_switch(SW_INVOL | SWT_NEEDRESCHED, NULL);
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thread_unlock(td);
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#ifdef KTRACE
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if (KTRPOINT(td, KTR_CSW))
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ktrcsw(0, 1, __func__);
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#endif
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}
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/*
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* Check for signals. Unlocked reads of p_pendingcnt or
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* p_siglist might cause process-directed signal to be handled
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* later.
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*/
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if (flags & TDF_NEEDSIGCHK || p->p_pendingcnt > 0 ||
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!SIGISEMPTY(p->p_siglist)) {
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PROC_LOCK(p);
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mtx_lock(&p->p_sigacts->ps_mtx);
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while ((sig = cursig(td)) != 0)
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postsig(sig);
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mtx_unlock(&p->p_sigacts->ps_mtx);
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PROC_UNLOCK(p);
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}
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/*
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* We need to check to see if we have to exit or wait due to a
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* single threading requirement or some other STOP condition.
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*/
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if (flags & TDF_NEEDSUSPCHK) {
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PROC_LOCK(p);
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thread_suspend_check(0);
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PROC_UNLOCK(p);
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}
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if (td->td_pflags & TDP_OLDMASK) {
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td->td_pflags &= ~TDP_OLDMASK;
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kern_sigprocmask(td, SIG_SETMASK, &td->td_oldsigmask, NULL, 0);
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}
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userret(td, framep);
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}
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const char *
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syscallname(struct proc *p, u_int code)
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{
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static const char unknown[] = "unknown";
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struct sysentvec *sv;
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sv = p->p_sysent;
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if (sv->sv_syscallnames == NULL || code >= sv->sv_size)
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return (unknown);
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return (sv->sv_syscallnames[code]);
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}
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