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 void (*tcp_hpts_softclock)(void);
80 * Define the code needed before returning to user mode, for trap and
84 userret(struct thread *td, struct trapframe *frame)
86 struct proc *p = td->td_proc;
88 CTR3(KTR_SYSC, "userret: thread %p (pid %d, %s)", td, p->p_pid,
90 KASSERT((p->p_flag & P_WEXIT) == 0,
91 ("Exiting process returns to usermode"));
94 * Check that we called signotify() enough. For
95 * multi-threaded processes, where signal distribution might
96 * change due to other threads changing sigmask, the check is
97 * racy and cannot be performed reliably.
98 * If current process is vfork child, indicated by P_PPWAIT, then
99 * issignal() ignores stops, so we block the check to avoid
100 * classifying pending signals.
102 if (p->p_numthreads == 1) {
105 if ((p->p_flag & P_PPWAIT) == 0 &&
106 (td->td_pflags & TDP_SIGFASTBLOCK) == 0 &&
107 SIGPENDING(td) && !td_ast_pending(td, TDA_AST) &&
108 !td_ast_pending(td, TDA_SIG)) {
111 "failed to set signal flags for ast p %p "
112 "td %p td_ast %#x fl %#x",
113 p, td, td->td_ast, td->td_flags);
121 * Charge system time if profiling.
123 if (__predict_false(p->p_flag & P_PROFIL))
124 addupc_task(td, TRAPF_PC(frame), td->td_pticks * psratio);
127 if (PMC_THREAD_HAS_SAMPLES(td))
128 PMC_CALL_HOOK(td, PMC_FN_THR_USERRET, NULL);
131 * Calling tcp_hpts_softclock() here allows us to avoid frequent,
132 * expensive callouts that trash the cache and lead to a much higher
133 * number of interrupts and context switches. Testing on busy web
134 * servers at Netflix has shown that this improves CPU use by 7% over
135 * relying only on callouts to drive HPTS, and also results in idle
136 * power savings on mostly idle servers.
137 * This was inspired by the paper "Soft Timers: Efficient Microsecond
138 * Software Timer Support for Network Processing"
139 * by Mohit Aron and Peter Druschel.
141 tcp_hpts_softclock();
143 * Let the scheduler adjust our priority etc.
148 * Check for misbehavior.
150 * In case there is a callchain tracing ongoing because of
151 * hwpmc(4), skip the scheduler pinning check.
152 * hwpmc(4) subsystem, infact, will collect callchain informations
153 * at ast() checkpoint, which is past userret().
155 WITNESS_WARN(WARN_PANIC, NULL, "userret: returning");
156 KASSERT(td->td_critnest == 0,
157 ("userret: Returning in a critical section"));
158 KASSERT(td->td_locks == 0,
159 ("userret: Returning with %d locks held", td->td_locks));
160 KASSERT(td->td_rw_rlocks == 0,
161 ("userret: Returning with %d rwlocks held in read mode",
163 KASSERT(td->td_sx_slocks == 0,
164 ("userret: Returning with %d sx locks held in shared mode",
166 KASSERT(td->td_lk_slocks == 0,
167 ("userret: Returning with %d lockmanager locks held in shared mode",
169 KASSERT((td->td_pflags & TDP_NOFAULTING) == 0,
170 ("userret: Returning with pagefaults disabled"));
171 if (__predict_false(!THREAD_CAN_SLEEP())) {
173 epoch_trace_list(curthread);
175 KASSERT(0, ("userret: Returning with sleep disabled"));
177 KASSERT(td->td_pinned == 0 || (td->td_pflags & TDP_CALLCHAIN) != 0,
178 ("userret: Returning with pinned thread"));
179 KASSERT(td->td_vp_reserved == NULL,
180 ("userret: Returning with preallocated vnode"));
181 KASSERT((td->td_flags & (TDF_SBDRY | TDF_SEINTR | TDF_SERESTART)) == 0,
182 ("userret: Returning with stop signals deferred"));
183 KASSERT(td->td_vslock_sz == 0,
184 ("userret: Returning with vslock-wired space"));
186 /* Unfortunately td_vnet_lpush needs VNET_DEBUG. */
187 VNET_ASSERT(curvnet == NULL,
188 ("%s: Returning on td %p (pid %d, %s) with vnet %p set in %s",
189 __func__, td, p->p_pid, td->td_name, curvnet,
190 (td->td_vnet_lpush != NULL) ? td->td_vnet_lpush : "N/A"));
195 ast_prep(struct thread *td, int tda __unused)
199 if (td->td_cowgen != atomic_load_int(&td->td_proc->p_cowgen))
200 thread_cow_update(td);
207 void (*ae_f)(struct thread *td, int ast);
210 _Static_assert(TDAI(TDA_MAX) <= UINT_MAX, "Too many ASTs");
212 static struct ast_entry ast_entries[TDA_MAX] __read_mostly = {
213 [TDA_AST] = { .ae_f = ast_prep, .ae_flags = ASTR_UNCOND},
217 ast_register(int ast, int flags, int tdp,
218 void (*f)(struct thread *, int asts))
220 struct ast_entry *ae;
222 MPASS(ast < TDA_MAX);
223 MPASS((flags & ASTR_TDP) == 0 || ((flags & ASTR_ASTF_REQUIRED) != 0
224 && __bitcount(tdp) == 1));
225 ae = &ast_entries[ast];
226 MPASS(ae->ae_f == NULL);
227 ae->ae_flags = flags;
229 atomic_interrupt_fence();
234 * XXXKIB Note that the deregistration of an AST handler does not
235 * drain threads possibly executing it, which affects unloadable
236 * modules. The issue is either handled by the subsystem using
237 * handlers, or simply ignored. Fixing the problem is considered not
238 * worth the overhead.
241 ast_deregister(int ast)
243 struct ast_entry *ae;
245 MPASS(ast < TDA_MAX);
246 ae = &ast_entries[ast];
247 MPASS(ae->ae_f != NULL);
249 atomic_interrupt_fence();
255 ast_sched_locked(struct thread *td, int tda)
257 THREAD_LOCK_ASSERT(td, MA_OWNED);
258 MPASS(tda < TDA_MAX);
260 td->td_ast |= TDAI(tda);
264 ast_unsched_locked(struct thread *td, int tda)
266 THREAD_LOCK_ASSERT(td, MA_OWNED);
267 MPASS(tda < TDA_MAX);
269 td->td_ast &= ~TDAI(tda);
273 ast_sched(struct thread *td, int tda)
276 ast_sched_locked(td, tda);
281 ast_sched_mask(struct thread *td, int ast)
289 ast_handler_calc_tdp_run(struct thread *td, const struct ast_entry *ae)
291 return ((ae->ae_flags & ASTR_TDP) == 0 ||
292 (td->td_pflags & ae->ae_tdp) != 0);
296 * Process an asynchronous software trap.
299 ast_handler(struct thread *td, struct trapframe *framep, bool dtor)
301 struct ast_entry *ae;
302 void (*f)(struct thread *td, int asts);
306 if (framep != NULL) {
307 kmsan_mark(framep, sizeof(*framep), KMSAN_STATE_INITED);
308 td->td_frame = framep;
311 if (__predict_true(!dtor)) {
312 WITNESS_WARN(WARN_PANIC, NULL, "Returning to user mode");
313 mtx_assert(&Giant, MA_NOTOWNED);
314 THREAD_LOCK_ASSERT(td, MA_NOTOWNED);
317 * This updates the td_ast for the checks below in one
318 * atomic operation with turning off all scheduled AST's.
319 * If another AST is triggered while we are handling the
320 * AST's saved in td_ast, the td_ast is again non-zero and
321 * ast() will be called again.
329 * The td thread's td_lock is not guaranteed to exist,
330 * the thread might be not initialized enough when it's
331 * destructor is called. It is safe to read and
332 * update td_ast without locking since the thread is
333 * not runnable or visible to other threads.
339 CTR3(KTR_SYSC, "ast: thread %p (pid %d, %s)", td, td->td_proc->p_pid,
340 td->td_proc->p_comm);
341 KASSERT(framep == NULL || TRAPF_USERMODE(framep),
342 ("ast in kernel mode"));
344 for (a = 0; a < nitems(ast_entries); a++) {
345 ae = &ast_entries[a];
349 atomic_interrupt_fence();
352 if (__predict_false(framep == NULL)) {
353 if ((ae->ae_flags & ASTR_KCLEAR) != 0)
354 run = ast_handler_calc_tdp_run(td, ae);
356 if ((ae->ae_flags & ASTR_UNCOND) != 0)
358 else if ((ae->ae_flags & ASTR_ASTF_REQUIRED) != 0 &&
359 (td_ast & TDAI(a)) != 0)
360 run = ast_handler_calc_tdp_run(td, ae);
368 ast(struct trapframe *framep)
373 ast_handler(td, framep, false);
378 ast_kclear(struct thread *td)
380 ast_handler(td, NULL, td != curthread);
384 syscallname(struct proc *p, u_int code)
386 static const char unknown[] = "unknown";
387 struct sysentvec *sv;
390 if (sv->sv_syscallnames == NULL || code >= sv->sv_size)
392 return (sv->sv_syscallnames[code]);