16baf59c6d
An application can use the mere fact of epoll_wait returning an fd as synchronization with the write on the fd that triggered the notification. This pattern come up in an internal networking server (b/229276331). If an fd is added to epoll, setup a link from the fd to the epoll fd and use it for synchronization as well. Reviewed By: melver Differential Revision: https://reviews.llvm.org/D124518
43 lines
1.3 KiB
C++
43 lines
1.3 KiB
C++
// RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
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// The test captures what some high-performance networking servers do.
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// One thread writes to an fd, and another just receives an epoll
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// notification about the write to synchronize with the first thread
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// w/o actually reading from the fd.
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#include "../test.h"
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#include <errno.h>
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#include <sys/epoll.h>
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#include <sys/eventfd.h>
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int main() {
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int efd = epoll_create(1);
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if (efd == -1)
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exit(printf("epoll_create failed: %d\n", errno));
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int fd = eventfd(0, 0);
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if (fd == -1)
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exit(printf("eventfd failed: %d\n", errno));
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epoll_event event = {.events = EPOLLIN | EPOLLET};
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if (epoll_ctl(efd, EPOLL_CTL_ADD, fd, &event))
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exit(printf("epoll_ctl failed: %d\n", errno));
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pthread_t th;
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pthread_create(
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&th, nullptr,
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+[](void *arg) -> void * {
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long long to_add = 1;
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if (write((long)arg, &to_add, sizeof(to_add)) != sizeof(to_add))
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exit(printf("write failed: %d\n", errno));
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return nullptr;
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},
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(void *)(long)fd);
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struct epoll_event events[1] = {};
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if (epoll_wait(efd, events, 1, -1) != 1)
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exit(printf("epoll_wait failed: %d\n", errno));
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close(fd);
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pthread_join(th, nullptr);
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close(efd);
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fprintf(stderr, "DONE\n");
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}
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// CHECK: DONE
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