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https://github.com/golang/go
synced 2024-10-05 00:21:21 -06:00
532dee3842
Signal handlers are global resources but many language environments (Go, C++ at Google, etc) assume they have sole ownership of a particular handler. Signal handlers in mixed-language applications must therefore be robust against unexpected delivery of certain signals, such as SIGPROF. The default Go signal handler runtime·sigtramp assumes that it will never be called on a non-Go thread, but this assumption is violated by when linking in C++ code that spawns threads. Specifically, the handler asserts the thread has an associated "m" (Go scheduler). This CL is a very simple workaround: discard SIGPROF delivered to non-Go threads. runtime.badsignal(int32) now receives the signal number; if it returns without panicking (e.g. sig==SIGPROF) the signal is discarded. I don't think there is any really satisfactory solution to the problem of signal-based profiling in a mixed-language application. It's not only the issue of handler clobbering, but also that a C++ SIGPROF handler called in a Go thread can't unwind the Go stack (and vice versa). The best we can hope for is not crashing. Note: - I've ported this to all POSIX platforms, except ARM-linux which already ignores unexpected signals on m-less threads. - I've avoided tail-calling runtime.badsignal because AFAICT the 6a/6l don't support it. - I've avoided hoisting 'push sig' (common to both function calls) because it makes the code harder to read. - Fixed an (apparently incorrect?) docstring. R=iant, rsc, minux.ma CC=golang-dev https://golang.org/cl/6498057
222 lines
5.1 KiB
C
222 lines
5.1 KiB
C
// Use of this source file is governed by a BSD-style
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// license that can be found in the LICENSE file.`
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#include "runtime.h"
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#include "defs_GOOS_GOARCH.h"
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#include "os_GOOS.h"
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#include "stack.h"
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extern SigTab runtime·sigtab[];
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extern int32 runtime·sys_umtx_op(uint32*, int32, uint32, void*, void*);
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// From FreeBSD's <sys/sysctl.h>
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#define CTL_HW 6
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#define HW_NCPU 3
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static Sigset sigset_all = { ~(uint32)0, ~(uint32)0, ~(uint32)0, ~(uint32)0, };
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static Sigset sigset_none = { 0, 0, 0, 0, };
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static int32
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getncpu(void)
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{
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uint32 mib[2];
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uint32 out;
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int32 ret;
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uintptr nout;
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// Fetch hw.ncpu via sysctl.
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mib[0] = CTL_HW;
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mib[1] = HW_NCPU;
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nout = sizeof out;
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out = 0;
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ret = runtime·sysctl(mib, 2, (byte*)&out, &nout, nil, 0);
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if(ret >= 0)
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return out;
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else
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return 1;
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}
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// FreeBSD's umtx_op syscall is effectively the same as Linux's futex, and
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// thus the code is largely similar. See linux/thread.c and lock_futex.c for comments.
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void
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runtime·futexsleep(uint32 *addr, uint32 val, int64 ns)
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{
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int32 ret;
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Timespec ts, *tsp;
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if(ns < 0)
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tsp = nil;
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else {
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ts.tv_sec = ns / 1000000000LL;
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ts.tv_nsec = ns % 1000000000LL;
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tsp = &ts;
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}
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ret = runtime·sys_umtx_op(addr, UMTX_OP_WAIT, val, nil, tsp);
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if(ret >= 0 || ret == -EINTR)
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return;
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runtime·printf("umtx_wait addr=%p val=%d ret=%d\n", addr, val, ret);
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*(int32*)0x1005 = 0x1005;
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}
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void
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runtime·futexwakeup(uint32 *addr, uint32 cnt)
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{
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int32 ret;
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ret = runtime·sys_umtx_op(addr, UMTX_OP_WAKE, cnt, nil, nil);
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if(ret >= 0)
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return;
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runtime·printf("umtx_wake addr=%p ret=%d\n", addr, ret);
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*(int32*)0x1006 = 0x1006;
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}
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void runtime·thr_start(void*);
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void
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runtime·newosproc(M *m, G *g, void *stk, void (*fn)(void))
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{
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ThrParam param;
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Sigset oset;
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USED(fn); // thr_start assumes fn == mstart
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USED(g); // thr_start assumes g == m->g0
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if(0){
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runtime·printf("newosproc stk=%p m=%p g=%p fn=%p id=%d/%d ostk=%p\n",
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stk, m, g, fn, m->id, m->tls[0], &m);
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}
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runtime·sigprocmask(&sigset_all, &oset);
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runtime·memclr((byte*)¶m, sizeof param);
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param.start_func = runtime·thr_start;
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param.arg = m;
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param.stack_base = (int8*)g->stackbase;
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param.stack_size = (byte*)stk - (byte*)g->stackbase;
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param.child_tid = (intptr*)&m->procid;
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param.parent_tid = nil;
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param.tls_base = (int8*)&m->tls[0];
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param.tls_size = sizeof m->tls;
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m->tls[0] = m->id; // so 386 asm can find it
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runtime·thr_new(¶m, sizeof param);
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runtime·sigprocmask(&oset, nil);
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}
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void
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runtime·osinit(void)
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{
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runtime·ncpu = getncpu();
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}
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void
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runtime·goenvs(void)
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{
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runtime·goenvs_unix();
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}
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// Called to initialize a new m (including the bootstrap m).
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void
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runtime·minit(void)
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{
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// Initialize signal handling
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m->gsignal = runtime·malg(32*1024);
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runtime·signalstack((byte*)m->gsignal->stackguard - StackGuard, 32*1024);
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runtime·sigprocmask(&sigset_none, nil);
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}
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void
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runtime·sigpanic(void)
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{
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switch(g->sig) {
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case SIGBUS:
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if(g->sigcode0 == BUS_ADRERR && g->sigcode1 < 0x1000) {
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if(g->sigpc == 0)
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runtime·panicstring("call of nil func value");
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runtime·panicstring("invalid memory address or nil pointer dereference");
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}
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runtime·printf("unexpected fault address %p\n", g->sigcode1);
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runtime·throw("fault");
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case SIGSEGV:
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if((g->sigcode0 == 0 || g->sigcode0 == SEGV_MAPERR || g->sigcode0 == SEGV_ACCERR) && g->sigcode1 < 0x1000) {
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if(g->sigpc == 0)
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runtime·panicstring("call of nil func value");
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runtime·panicstring("invalid memory address or nil pointer dereference");
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}
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runtime·printf("unexpected fault address %p\n", g->sigcode1);
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runtime·throw("fault");
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case SIGFPE:
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switch(g->sigcode0) {
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case FPE_INTDIV:
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runtime·panicstring("integer divide by zero");
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case FPE_INTOVF:
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runtime·panicstring("integer overflow");
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}
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runtime·panicstring("floating point error");
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}
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runtime·panicstring(runtime·sigtab[g->sig].name);
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}
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uintptr
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runtime·memlimit(void)
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{
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Rlimit rl;
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extern byte text[], end[];
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uintptr used;
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if(runtime·getrlimit(RLIMIT_AS, &rl) != 0)
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return 0;
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if(rl.rlim_cur >= 0x7fffffff)
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return 0;
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// Estimate our VM footprint excluding the heap.
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// Not an exact science: use size of binary plus
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// some room for thread stacks.
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used = end - text + (64<<20);
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if(used >= rl.rlim_cur)
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return 0;
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// If there's not at least 16 MB left, we're probably
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// not going to be able to do much. Treat as no limit.
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rl.rlim_cur -= used;
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if(rl.rlim_cur < (16<<20))
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return 0;
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return rl.rlim_cur - used;
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}
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void
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runtime·setprof(bool on)
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{
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USED(on);
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}
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static int8 badcallback[] = "runtime: cgo callback on thread not created by Go.\n";
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// This runs on a foreign stack, without an m or a g. No stack split.
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#pragma textflag 7
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void
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runtime·badcallback(void)
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{
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runtime·write(2, badcallback, sizeof badcallback - 1);
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}
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static int8 badsignal[] = "runtime: signal received on thread not created by Go.\n";
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// This runs on a foreign stack, without an m or a g. No stack split.
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#pragma textflag 7
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void
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runtime·badsignal(int32 sig)
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{
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if (sig == SIGPROF) {
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return; // Ignore SIGPROFs intended for a non-Go thread.
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}
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runtime·write(2, badsignal, sizeof badsignal - 1);
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runtime·exit(1);
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}
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