2 * SPDX-License-Identifier: BSD-4-Clause
4 * Copyright (C) 1994, David Greenman
5 * Copyright (c) 1990, 1993
6 * The Regents of the University of California. All rights reserved.
7 * Copyright (c) 2007, 2022 The FreeBSD Foundation
9 * This code is derived from software contributed to Berkeley by
10 * the University of Utah, and William Jolitz.
12 * Portions of this software were developed by A. Joseph Koshy under
13 * sponsorship from the FreeBSD Foundation and Google, Inc.
15 * Redistribution and use in source and binary forms, with or without
16 * modification, are permitted provided that the following conditions
18 * 1. Redistributions of source code must retain the above copyright
19 * notice, this list of conditions and the following disclaimer.
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in the
22 * documentation and/or other materials provided with the distribution.
23 * 3. All advertising materials mentioning features or use of this software
24 * must display the following acknowledgement:
25 * This product includes software developed by the University of
26 * California, Berkeley and its contributors.
27 * 4. Neither the name of the University nor the names of its contributors
28 * may be used to endorse or promote products derived from this software
29 * without specific prior written permission.
31 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
32 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
33 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
34 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
35 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
36 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
37 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
39 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
40 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
44 #include <sys/cdefs.h>
45 #include "opt_hwpmc_hooks.h"
47 #include <sys/param.h>
48 #include <sys/kernel.h>
49 #include <sys/limits.h>
52 #include <sys/mutex.h>
55 #include <sys/resourcevar.h>
56 #include <sys/sched.h>
57 #include <sys/syscall.h>
58 #include <sys/syscallsubr.h>
59 #include <sys/sysent.h>
60 #include <sys/systm.h>
61 #include <sys/vmmeter.h>
63 #include <machine/cpu.h>
70 #include <sys/pmckern.h>
74 #include <sys/epoch.h>
77 volatile uint32_t __read_frequently hpts_that_need_softclock = 0;
79 void (*tcp_hpts_softclock)(void);
82 * Define the code needed before returning to user mode, for trap and
86 userret(struct thread *td, struct trapframe *frame)
88 struct proc *p = td->td_proc;
90 CTR3(KTR_SYSC, "userret: thread %p (pid %d, %s)", td, p->p_pid,
92 KASSERT((p->p_flag & P_WEXIT) == 0,
93 ("Exiting process returns to usermode"));
96 * Check that we called signotify() enough. For
97 * multi-threaded processes, where signal distribution might
98 * change due to other threads changing sigmask, the check is
99 * racy and cannot be performed reliably.
100 * If current process is vfork child, indicated by P_PPWAIT, then
101 * issignal() ignores stops, so we block the check to avoid
102 * classifying pending signals.
104 if (p->p_numthreads == 1) {
107 if ((p->p_flag & P_PPWAIT) == 0 &&
108 (td->td_pflags & TDP_SIGFASTBLOCK) == 0 &&
109 SIGPENDING(td) && !td_ast_pending(td, TDA_AST) &&
110 !td_ast_pending(td, TDA_SIG)) {
113 "failed to set signal flags for ast p %p "
114 "td %p td_ast %#x fl %#x",
115 p, td, td->td_ast, td->td_flags);
123 * Charge system time if profiling.
125 if (__predict_false(p->p_flag & P_PROFIL))
126 addupc_task(td, TRAPF_PC(frame), td->td_pticks * psratio);
129 if (PMC_THREAD_HAS_SAMPLES(td))
130 PMC_CALL_HOOK(td, PMC_FN_THR_USERRET, NULL);
133 * Calling tcp_hpts_softclock() here allows us to avoid frequent,
134 * expensive callouts that trash the cache and lead to a much higher
135 * number of interrupts and context switches. Testing on busy web
136 * servers at Netflix has shown that this improves CPU use by 7% over
137 * relying only on callouts to drive HPTS, and also results in idle
138 * power savings on mostly idle servers.
139 * This was inspired by the paper "Soft Timers: Efficient Microsecond
140 * Software Timer Support for Network Processing"
141 * by Mohit Aron and Peter Druschel.
143 tcp_hpts_softclock();
145 * Let the scheduler adjust our priority etc.
150 * Check for misbehavior.
152 * In case there is a callchain tracing ongoing because of
153 * hwpmc(4), skip the scheduler pinning check.
154 * hwpmc(4) subsystem, infact, will collect callchain informations
155 * at ast() checkpoint, which is past userret().
157 WITNESS_WARN(WARN_PANIC, NULL, "userret: returning");
158 KASSERT(td->td_critnest == 0,
159 ("userret: Returning in a critical section"));
160 KASSERT(td->td_locks == 0,
161 ("userret: Returning with %d locks held", td->td_locks));
162 KASSERT(td->td_rw_rlocks == 0,
163 ("userret: Returning with %d rwlocks held in read mode",
165 KASSERT(td->td_sx_slocks == 0,
166 ("userret: Returning with %d sx locks held in shared mode",
168 KASSERT(td->td_lk_slocks == 0,
169 ("userret: Returning with %d lockmanager locks held in shared mode",
171 KASSERT((td->td_pflags & TDP_NOFAULTING) == 0,
172 ("userret: Returning with pagefaults disabled"));
173 if (__predict_false(!THREAD_CAN_SLEEP())) {
175 epoch_trace_list(curthread);
177 KASSERT(0, ("userret: Returning with sleep disabled"));
179 KASSERT(td->td_pinned == 0 || (td->td_pflags & TDP_CALLCHAIN) != 0,
180 ("userret: Returning with pinned thread"));
181 KASSERT(td->td_vp_reserved == NULL,
182 ("userret: Returning with preallocated vnode"));
183 KASSERT((td->td_flags & (TDF_SBDRY | TDF_SEINTR | TDF_SERESTART)) == 0,
184 ("userret: Returning with stop signals deferred"));
185 KASSERT(td->td_vslock_sz == 0,
186 ("userret: Returning with vslock-wired space"));
188 /* Unfortunately td_vnet_lpush needs VNET_DEBUG. */
189 VNET_ASSERT(curvnet == NULL,
190 ("%s: Returning on td %p (pid %d, %s) with vnet %p set in %s",
191 __func__, td, p->p_pid, td->td_name, curvnet,
192 (td->td_vnet_lpush != NULL) ? td->td_vnet_lpush : "N/A"));
197 ast_prep(struct thread *td, int tda __unused)
201 if (td->td_cowgen != atomic_load_int(&td->td_proc->p_cowgen))
202 thread_cow_update(td);
209 void (*ae_f)(struct thread *td, int ast);
212 _Static_assert(TDAI(TDA_MAX) <= UINT_MAX, "Too many ASTs");
214 static struct ast_entry ast_entries[TDA_MAX] __read_mostly = {
215 [TDA_AST] = { .ae_f = ast_prep, .ae_flags = ASTR_UNCOND},
219 ast_register(int ast, int flags, int tdp,
220 void (*f)(struct thread *, int asts))
222 struct ast_entry *ae;
224 MPASS(ast < TDA_MAX);
225 MPASS((flags & ASTR_TDP) == 0 || ((flags & ASTR_ASTF_REQUIRED) != 0
226 && __bitcount(tdp) == 1));
227 ae = &ast_entries[ast];
228 MPASS(ae->ae_f == NULL);
229 ae->ae_flags = flags;
231 atomic_interrupt_fence();
236 * XXXKIB Note that the deregistration of an AST handler does not
237 * drain threads possibly executing it, which affects unloadable
238 * modules. The issue is either handled by the subsystem using
239 * handlers, or simply ignored. Fixing the problem is considered not
240 * worth the overhead.
243 ast_deregister(int ast)
245 struct ast_entry *ae;
247 MPASS(ast < TDA_MAX);
248 ae = &ast_entries[ast];
249 MPASS(ae->ae_f != NULL);
251 atomic_interrupt_fence();
257 ast_sched_locked(struct thread *td, int tda)
259 THREAD_LOCK_ASSERT(td, MA_OWNED);
260 MPASS(tda < TDA_MAX);
262 td->td_ast |= TDAI(tda);
266 ast_unsched_locked(struct thread *td, int tda)
268 THREAD_LOCK_ASSERT(td, MA_OWNED);
269 MPASS(tda < TDA_MAX);
271 td->td_ast &= ~TDAI(tda);
275 ast_sched(struct thread *td, int tda)
278 ast_sched_locked(td, tda);
283 ast_sched_mask(struct thread *td, int ast)
291 ast_handler_calc_tdp_run(struct thread *td, const struct ast_entry *ae)
293 return ((ae->ae_flags & ASTR_TDP) == 0 ||
294 (td->td_pflags & ae->ae_tdp) != 0);
298 * Process an asynchronous software trap.
301 ast_handler(struct thread *td, struct trapframe *framep, bool dtor)
303 struct ast_entry *ae;
304 void (*f)(struct thread *td, int asts);
308 if (framep != NULL) {
309 kmsan_mark(framep, sizeof(*framep), KMSAN_STATE_INITED);
310 td->td_frame = framep;
313 if (__predict_true(!dtor)) {
314 WITNESS_WARN(WARN_PANIC, NULL, "Returning to user mode");
315 mtx_assert(&Giant, MA_NOTOWNED);
316 THREAD_LOCK_ASSERT(td, MA_NOTOWNED);
319 * This updates the td_ast for the checks below in one
320 * atomic operation with turning off all scheduled AST's.
321 * If another AST is triggered while we are handling the
322 * AST's saved in td_ast, the td_ast is again non-zero and
323 * ast() will be called again.
331 * The td thread's td_lock is not guaranteed to exist,
332 * the thread might be not initialized enough when it's
333 * destructor is called. It is safe to read and
334 * update td_ast without locking since the thread is
335 * not runnable or visible to other threads.
341 CTR3(KTR_SYSC, "ast: thread %p (pid %d, %s)", td, td->td_proc->p_pid,
342 td->td_proc->p_comm);
343 KASSERT(framep == NULL || TRAPF_USERMODE(framep),
344 ("ast in kernel mode"));
346 for (a = 0; a < nitems(ast_entries); a++) {
347 ae = &ast_entries[a];
351 atomic_interrupt_fence();
354 if (__predict_false(framep == NULL)) {
355 if ((ae->ae_flags & ASTR_KCLEAR) != 0)
356 run = ast_handler_calc_tdp_run(td, ae);
358 if ((ae->ae_flags & ASTR_UNCOND) != 0)
360 else if ((ae->ae_flags & ASTR_ASTF_REQUIRED) != 0 &&
361 (td_ast & TDAI(a)) != 0)
362 run = ast_handler_calc_tdp_run(td, ae);
370 ast(struct trapframe *framep)
375 ast_handler(td, framep, false);
380 ast_kclear(struct thread *td)
382 ast_handler(td, NULL, td != curthread);
386 syscallname(struct proc *p, u_int code)
388 static const char unknown[] = "unknown";
389 struct sysentvec *sv;
392 if (sv->sv_syscallnames == NULL || code >= sv->sv_size)
394 return (sv->sv_syscallnames[code]);