forked from OSchip/llvm-project
56 lines
1.7 KiB
C++
56 lines
1.7 KiB
C++
// RUN: %clangxx -O1 %s -o %t && TSAN_OPTIONS="flush_memory_ms=1 memory_limit_mb=1" %run %t 2>&1 | FileCheck %s
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// JVM uses SEGV to preempt threads. All threads do a load from a known address
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// periodically. When runtime needs to preempt threads, it unmaps the page.
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// Threads start triggering SEGV one by one. The signal handler blocks
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// threads while runtime does its thing. Then runtime maps the page again
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// and resumes the threads.
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// Previously this pattern conflicted with stop-the-world machinery,
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// because it briefly reset SEGV handler to SIG_DFL.
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// As the consequence JVM just silently died.
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// This test sets memory flushing rate to maximum, then does series of
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// "benign" SEGVs that are handled by signal handler, and ensures that
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// the process survive.
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#include <assert.h>
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#include <signal.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <unistd.h>
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unsigned long page_size;
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void *guard;
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void handler(int signo, siginfo_t *info, void *uctx) {
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mprotect(guard, page_size, PROT_READ | PROT_WRITE);
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}
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int main() {
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page_size = sysconf(_SC_PAGESIZE);
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struct sigaction a, old;
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memset(&a, 0, sizeof(a));
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memset(&old, 0, sizeof(old));
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a.sa_sigaction = handler;
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a.sa_flags = SA_SIGINFO;
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sigaction(SIGSEGV, &a, &old);
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memset(&a, 0, sizeof(a));
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sigaction(SIGSEGV, 0, &a);
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assert(a.sa_sigaction == handler);
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assert(a.sa_flags & SA_SIGINFO);
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guard = mmap(0, 3 * page_size, PROT_NONE, MAP_ANON | MAP_PRIVATE, -1, 0);
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guard = (char*)guard + page_size; // work around a kernel bug
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for (int i = 0; i < 1000000; i++) {
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mprotect(guard, page_size, PROT_NONE);
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*(int*)guard = 1;
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}
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sigaction(SIGSEGV, &old, 0);
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fprintf(stderr, "DONE\n");
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}
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// CHECK: DONE
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