swift-nio: Too many calls to futex

Expected behavior

I expect there not to be so many futex calls.

Actual behavior

916   20:12:30 epoll_create(128)        = 3 <0.000055>                                                                                                                         
916   20:12:30 futex(0x667b10, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000023>
916   20:12:30 futex(0x667b20, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000033>
916   20:12:30 eventfd2(0, EFD_CLOEXEC|EFD_NONBLOCK) = 4 <0.000064>
916   20:12:30 futex(0x667af0, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000032>
916   20:12:30 futex(0x667b00, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000022>
916   20:12:30 timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC|TFD_NONBLOCK) = 5 <0.000058>
916   20:12:30 futex(0x667b60, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000022>
916   20:12:30 futex(0x667b80, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000033>
916   20:12:30 futex(0x667b90, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000032>
916   20:12:30 futex(0x667b30, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000023>
916   20:12:30 epoll_ctl(3, EPOLL_CTL_ADD, 4, {EPOLLIN|EPOLLERR|EPOLLRDHUP, {u32=4, u64=4}}) = 0 <0.000068>
916   20:12:30 futex(0x667ba0, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000020>
916   20:12:30 epoll_ctl(3, EPOLL_CTL_ADD, 5, {EPOLLIN|EPOLLERR|EPOLLRDHUP|EPOLLET, {u32=5, u64=5}}) = 0 <0.000053>
916   20:12:30 futex(0x6686c8, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000068>
916   20:12:30 futex(0x6680b0, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000056>
916   20:12:30 futex(0x7f81323e9530, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000064>
916   20:12:30 futex(0x7f81323e9928, FUTEX_WAKE_PRIVATE, 2147483647) = 0 <0.000068>

Steps to reproduce

  1. docker run --security-opt seccomp:unconfined -v$CWD:/code -it --rm swiftnio
  2. cd /code && swift build
  3. strace -s 1024 -fF -tT -o trace.out ./.build/x86_64-unknown-linux/debug/NIOHTTP1Server 0.0.0.0 8888 .

If possible, minimal yet complete reproducer code (or URL to code)

There are no futex calls here:

root@1ba3a0b6d2c0:/code# cat epoll.c 
#include <sys/epoll.h>

int main() {
    int fd = epoll_create(1);
    epoll_wait(fd, 0, 0, 0);
    return 0;
}
root@1ba3a0b6d2c0:/code# clang epoll.c 
root@1ba3a0b6d2c0:/code# strace -s 1024 -f -tT ./a.out 
21:46:15 execve("./a.out", ["./a.out"], [/* 11 vars */]) = 0 <0.001591>
21:46:15 brk(NULL)                      = 0x1c96000 <0.000028>
21:46:15 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) <0.000200>
21:46:15 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) <0.000012>
21:46:15 open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3 <0.000253>
21:46:15 fstat(3, {st_mode=S_IFREG|0644, st_size=18870, ...}) = 0 <0.000017>
21:46:15 mmap(NULL, 18870, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f74ce3e6000 <0.000023>
21:46:15 close(3)                       = 0 <0.000015>
21:46:15 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) <0.000036>
21:46:15 open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3 <0.000022>
21:46:15 read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0P\t\2\0\0\0\0\0@\0\0\0\0\0\0\0\270r\34\0\0\0\0\0\0\0\0\0@\0008\0\n\0@\0H\0G\0\6\0\0\0\5\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0000\2\0\0\0\0\0\0000\2\0\0\0\0\0\0\10\0\0\0\0\0\0\0\3\0\0\0\4\0\0\0`f\31\0\0\0\0\0`f\31\0\0\0\0\0`f\31\0\0\0\0\0\34\0\0\0\0\0\0\0\34\0\0\0\0\0\0\0\20\0\0\0\0\0\0\0\1\0\0\0\5\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\20\373\33\0\0\0\0\0\20\373\33\0\0\0\0\0\0\0 \0\0\0\0\0\1\0\0\0\6\0\0\0\300\7\34\0\0\0\0\0\300\7<\0\0\0\0\0\300\7<\0\0\0\0\0`O\0\0\0\0\0\0\340\221\0\0\0\0\0\0\0\0 \0\0\0\0\0\2\0\0\0\6\0\0\0\240;\34\0\0\0\0\0\240;<\0\0\0\0\0\240;<\0\0\0\0\0\340\1\0\0\0\0\0\0\340\1\0\0\0\0\0\0\10\0\0\0\0\0\0\0\4\0\0\0\4\0\0\0p\2\0\0\0\0\0\0p\2\0\0\0\0\0\0p\2\0\0\0\0\0\0D\0\0\0\0\0\0\0D\0\0\0\0\0\0\0\4\0\0\0\0\0\0\0\7\0\0\0\4\0\0\0\300\7\34\0\0\0\0\0\300\7<\0\0\0\0\0\300\7<\0\0\0\0\0\20\0\0\0\0\0\0\0x\0\0\0\0\0\0\0\10\0\0\0\0\0\0\0P\345td\4\0\0\0|f\31\0\0\0\0\0|f\31\0\0\0\0\0|f\31\0\0\0\0\0\274T\0\0\0\0\0\0\274T\0\0\0\0\0\0\4\0\0\0\0\0\0\0Q\345td\6\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\20\0\0\0\0\0\0\0R\345td\4\0\0\0\300\7\34\0\0\0\0\0\300\7<\0\0\0\0\0\300\7<\0\0\0\0\0@8\0\0\0\0\0\0@8\0\0\0\0\0\0\1\0\0\0\0\0\0\0\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\2658\32Ey\6\322y\0078\"\245\316\262LK\376\371M\333\4\0\0\0\20\0\0\0\1\0\0\0GNU\0\0\0\0\0\2\0\0\0\6\0\0\0 \0\0\0\0\0\0\0\363\3\0\0\n\0\0\0\0\1\0\0\16\0\0\0\0000\20D\240 \2\1\210\3\346\220\305E\214\0\304\0\10\0\5\204\0`\300\200\0\r\212\f\0\4\20\0\210@2\10*@\210T<, \0162H&\204\300\214\4\10\0\2\2\16\241\254\32\4f\300\0\3002\0\300\0P\1 \201\10\204\v  ($\0\4 Z\0\20X\200\312DB(\0\6\200\20\30B\0 @\200\0IP\0Q\212@\22\0\0\0\0\10\0\0\21\20", 832) = 832 <0.000024>
21:46:15 fstat(3, {st_mode=S_IFREG|0755, st_size=1868984, ...}) = 0 <0.000013>
21:46:15 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f74ce3e5000 <0.000111>
21:46:15 mmap(NULL, 3971488, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f74cddfc000 <0.000057>
21:46:15 mprotect(0x7f74cdfbc000, 2097152, PROT_NONE) = 0 <0.000041>
21:46:15 mmap(0x7f74ce1bc000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1c0000) = 0x7f74ce1bc000 <0.000044>
21:46:15 mmap(0x7f74ce1c2000, 14752, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f74ce1c2000 <0.000019>
21:46:15 close(3)                       = 0 <0.000013>
21:46:15 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f74ce3e4000 <0.000020>
21:46:15 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f74ce3e3000 <0.000011>
21:46:15 arch_prctl(ARCH_SET_FS, 0x7f74ce3e4700) = 0 <0.000159>
21:46:15 mprotect(0x7f74ce1bc000, 16384, PROT_READ) = 0 <0.000030>
21:46:15 mprotect(0x600000, 4096, PROT_READ) = 0 <0.000068>
21:46:15 mprotect(0x7f74ce3eb000, 4096, PROT_READ) = 0 <0.000024>
21:46:15 munmap(0x7f74ce3e6000, 18870)  = 0 <0.000019>
21:46:15 epoll_create(1)                = 3 <0.000044>
21:46:15 epoll_wait(3, NULL, 0, 0)      = -1 EINVAL (Invalid argument) <0.000015>
21:46:15 exit_group(0)                  = ?
21:46:15 +++ exited with 0 +++

SwiftNIO version/commit hash

c8d198020717b8bbb4c3be4e47c06aab4085c7fc

Swift & OS version (output of swift --version && uname -a)

Swift version 4.0 (swift-4.0-RELEASE) Target: x86_64-unknown-linux-gnu Linux 1ba3a0b6d2c0 4.9.60-linuxkit-aufs #1 SMP Mon Nov 6 16:00:12 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

About this issue

  • Original URL
  • State: closed
  • Created 6 years ago
  • Reactions: 2
  • Comments: 15 (13 by maintainers)

Commits related to this issue

Most upvoted comments

I introduced pthreads just to be sure:

root@1ba3a0b6d2c0:/code# cat epoll.c 
#include <sys/epoll.h>
#include <pthread.h>

static void *start(void *arg) {
    for (int i=0; i<10; i++) {
        int fd = epoll_create(1);
        epoll_wait(fd, 0, 0, 0);
    }
    return 0;
}

int main() {
    pthread_t thread;
    pthread_create(&thread, 0, start, 0);
    pthread_join(thread, 0);
    return 0;
}
root@1ba3a0b6d2c0:/code# clang -pthread epoll.c 
root@1ba3a0b6d2c0:/code# strace -s 1024 -f -tT ./a.out
22:03:51 execve("./a.out", ["./a.out"], [/* 11 vars */]) = 0 <0.002773>
22:03:51 brk(NULL)                      = 0xb81000 <0.000168>
22:03:51 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) <0.000044>
22:03:51 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory) <0.000124>
22:03:51 open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3 <0.000055>
22:03:51 fstat(3, {st_mode=S_IFREG|0644, st_size=18870, ...}) = 0 <0.000230>
22:03:51 mmap(NULL, 18870, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce60f39000 <0.000470>
22:03:51 close(3)                       = 0 <0.000312>
22:03:51 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) <0.000311>
22:03:51 open("/lib/x86_64-linux-gnu/libpthread.so.0", O_RDONLY|O_CLOEXEC) = 3 <0.000384>
22:03:51 read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\260`\0\0\0\0\0\0@\0\0\0\0\0\0\0\210\23\2\0\0\0\0\0\0\0\0\0@\0008\0\t\0@\0)\0&\0\6\0\0\0\5\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0\370\1\0\0\0\0\0\0\370\1\0\0\0\0\0\0\10\0\0\0\0\0\0\0\3\0\0\0\4\0\0\0\2206\1\0\0\0\0\0\2206\1\0\0\0\0\0\2206\1\0\0\0\0\0\34\0\0\0\0\0\0\0\34\0\0\0\0\0\0\0\20\0\0\0\0\0\0\0\1\0\0\0\5\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\204y\1\0\0\0\0\0\204y\1\0\0\0\0\0\0\0 \0\0\0\0\0\1\0\0\0\6\0\0\0x{\1\0\0\0\0\0x{!\0\0\0\0\0x{!\0\0\0\0\0(\7\0\0\0\0\0\0\260H\0\0\0\0\0\0\0\0 \0\0\0\0\0\2\0\0\0\6\0\0\0P}\1\0\0\0\0\0P}!\0\0\0\0\0P}!\0\0\0\0\0000\2\0\0\0\0\0\0000\2\0\0\0\0\0\0\10\0\0\0\0\0\0\0\4\0\0\0\4\0\0\0008\2\0\0\0\0\0\0008\2\0\0\0\0\0\0008\2\0\0\0\0\0\0D\0\0\0\0\0\0\0D\0\0\0\0\0\0\0\4\0\0\0\0\0\0\0P\345td\4\0\0\0\2606\1\0\0\0\0\0\2606\1\0\0\0\0\0\2606\1\0\0\0\0\0\214\10\0\0\0\0\0\0\214\10\0\0\0\0\0\0\4\0\0\0\0\0\0\0Q\345td\6\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\20\0\0\0\0\0\0\0R\345td\4\0\0\0x{\1\0\0\0\0\0x{!\0\0\0\0\0x{!\0\0\0\0\0\210\4\0\0\0\0\0\0\210\4\0\0\0\0\0\0\1\0\0\0\0\0\0\0\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\316\27\340#T\"e\374\21\331\274\217SK\264\360pI=0\4\0\0\0\20\0\0\0\1\0\0\0GNU\0\0\0\0\0\2\0\0\0\6\0\0\0 \0\0\0\0\0\0\0\345\1\0\0W\0\0\0 \0\0\0\v\0\0\0\31#\2\261\1\10\20\2@@a\370\3\10\10\25\200 \0\0\0\0\200\300\321Q\0\0\0\22\353\3020D\0\10\20A\0\2\0\2\f\1\200\v\221\1\330\240\r\240@\230 \244\200\21\n\202-l@g\214V\24\0\224 \200$H\200P(\1\22\f\311B\240\220\22\10\f \2ZdA\245c\4@\n\n\n\0\2009\1(\314D\204\201\300\22\10(\fD\0\0\0\200Q\10\200\35\4B\320\2608A\0\1\0\0\265\0300\0\200`\2\20\"\0\tA\20\1\5\0P(\251\22G(\0\0\202\4\230@\4\0\20\340T\0\2@\2\2\20\3010f\26\200\0", 832) = 832 <0.000511>
22:03:51 fstat(3, {st_mode=S_IFREG|0755, st_size=138696, ...}) = 0 <0.000057>
22:03:51 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fce60f38000 <0.000038>
22:03:51 mmap(NULL, 2212904, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fce60afc000 <0.000175>
22:03:51 mprotect(0x7fce60b14000, 2093056, PROT_NONE) = 0 <0.000482>
22:03:51 mmap(0x7fce60d13000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x17000) = 0x7fce60d13000 <0.000815>
22:03:51 mmap(0x7fce60d15000, 13352, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fce60d15000 <0.000049>
22:03:51 close(3)                       = 0 <0.000236>
22:03:51 access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory) <0.000034>
22:03:51 open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3 <0.000046>
22:03:51 read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0P\t\2\0\0\0\0\0@\0\0\0\0\0\0\0\270r\34\0\0\0\0\0\0\0\0\0@\0008\0\n\0@\0H\0G\0\6\0\0\0\5\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0@\0\0\0\0\0\0\0000\2\0\0\0\0\0\0000\2\0\0\0\0\0\0\10\0\0\0\0\0\0\0\3\0\0\0\4\0\0\0`f\31\0\0\0\0\0`f\31\0\0\0\0\0`f\31\0\0\0\0\0\34\0\0\0\0\0\0\0\34\0\0\0\0\0\0\0\20\0\0\0\0\0\0\0\1\0\0\0\5\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\20\373\33\0\0\0\0\0\20\373\33\0\0\0\0\0\0\0 \0\0\0\0\0\1\0\0\0\6\0\0\0\300\7\34\0\0\0\0\0\300\7<\0\0\0\0\0\300\7<\0\0\0\0\0`O\0\0\0\0\0\0\340\221\0\0\0\0\0\0\0\0 \0\0\0\0\0\2\0\0\0\6\0\0\0\240;\34\0\0\0\0\0\240;<\0\0\0\0\0\240;<\0\0\0\0\0\340\1\0\0\0\0\0\0\340\1\0\0\0\0\0\0\10\0\0\0\0\0\0\0\4\0\0\0\4\0\0\0p\2\0\0\0\0\0\0p\2\0\0\0\0\0\0p\2\0\0\0\0\0\0D\0\0\0\0\0\0\0D\0\0\0\0\0\0\0\4\0\0\0\0\0\0\0\7\0\0\0\4\0\0\0\300\7\34\0\0\0\0\0\300\7<\0\0\0\0\0\300\7<\0\0\0\0\0\20\0\0\0\0\0\0\0x\0\0\0\0\0\0\0\10\0\0\0\0\0\0\0P\345td\4\0\0\0|f\31\0\0\0\0\0|f\31\0\0\0\0\0|f\31\0\0\0\0\0\274T\0\0\0\0\0\0\274T\0\0\0\0\0\0\4\0\0\0\0\0\0\0Q\345td\6\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\20\0\0\0\0\0\0\0R\345td\4\0\0\0\300\7\34\0\0\0\0\0\300\7<\0\0\0\0\0\300\7<\0\0\0\0\0@8\0\0\0\0\0\0@8\0\0\0\0\0\0\1\0\0\0\0\0\0\0\4\0\0\0\24\0\0\0\3\0\0\0GNU\0\2658\32Ey\6\322y\0078\"\245\316\262LK\376\371M\333\4\0\0\0\20\0\0\0\1\0\0\0GNU\0\0\0\0\0\2\0\0\0\6\0\0\0 \0\0\0\0\0\0\0\363\3\0\0\n\0\0\0\0\1\0\0\16\0\0\0\0000\20D\240 \2\1\210\3\346\220\305E\214\0\304\0\10\0\5\204\0`\300\200\0\r\212\f\0\4\20\0\210@2\10*@\210T<, \0162H&\204\300\214\4\10\0\2\2\16\241\254\32\4f\300\0\3002\0\300\0P\1 \201\10\204\v  ($\0\4 Z\0\20X\200\312DB(\0\6\200\20\30B\0 @\200\0IP\0Q\212@\22\0\0\0\0\10\0\0\21\20", 832) = 832 <0.000021>
22:03:51 fstat(3, {st_mode=S_IFREG|0755, st_size=1868984, ...}) = 0 <0.000020>
22:03:51 mmap(NULL, 3971488, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fce60732000 <0.000143>
22:03:51 mprotect(0x7fce608f2000, 2097152, PROT_NONE) = 0 <0.000027>
22:03:51 mmap(0x7fce60af2000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1c0000) = 0x7fce60af2000 <0.000054>
22:03:51 mmap(0x7fce60af8000, 14752, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fce60af8000 <0.000022>
22:03:51 close(3)                       = 0 <0.000026>
22:03:51 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fce60f37000 <0.000024>
22:03:51 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fce60f36000 <0.000022>
22:03:51 mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fce60f35000 <0.000101>
22:03:51 arch_prctl(ARCH_SET_FS, 0x7fce60f36700) = 0 <0.000019>
22:03:51 mprotect(0x7fce60af2000, 16384, PROT_READ) = 0 <0.000046>
22:03:51 mprotect(0x7fce60d13000, 4096, PROT_READ) = 0 <0.000022>
22:03:51 mprotect(0x600000, 4096, PROT_READ) = 0 <0.000033>
22:03:51 mprotect(0x7fce60f3e000, 4096, PROT_READ) = 0 <0.000190>
22:03:51 munmap(0x7fce60f39000, 18870)  = 0 <0.000103>
22:03:51 set_tid_address(0x7fce60f369d0) = 1750 <0.000011>
22:03:51 set_robust_list(0x7fce60f369e0, 24) = 0 <0.000014>
22:03:51 rt_sigaction(SIGRTMIN, {0x7fce60b01b50, [], SA_RESTORER|SA_SIGINFO, 0x7fce60b0d390}, NULL, 8) = 0 <0.000012>
22:03:51 rt_sigaction(SIGRT_1, {0x7fce60b01be0, [], SA_RESTORER|SA_RESTART|SA_SIGINFO, 0x7fce60b0d390}, NULL, 8) = 0 <0.000010>
22:03:51 rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0 <0.000083>
22:03:51 getrlimit(RLIMIT_STACK, {rlim_cur=8192*1024, rlim_max=RLIM64_INFINITY}) = 0 <0.000023>
22:03:51 mmap(NULL, 8392704, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_STACK, -1, 0) = 0x7fce5ff31000 <0.000014>
22:03:51 brk(NULL)                      = 0xb81000 <0.000011>
22:03:51 brk(0xba2000)                  = 0xba2000 <0.000024>
22:03:51 mprotect(0x7fce5ff31000, 4096, PROT_NONE) = 0 <0.000091>
22:03:51 clone(child_stack=0x7fce60730ff0, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x7fce607319d0, tls=0x7fce60731700, child_tidptr=0x7fce607319d0) = 1751 <0.000202>
22:03:51 futex(0x7fce607319d0, FUTEX_WAIT, 1751, NULLstrace: Process 1751 attached
 <unfinished ...>
[pid  1751] 22:03:51 set_robust_list(0x7fce607319e0, 24) = 0 <0.000111>
[pid  1751] 22:03:51 epoll_create(1)    = 3 <0.000179>
[pid  1751] 22:03:51 epoll_wait(3, NULL, 0, 0) = -1 EINVAL (Invalid argument) <0.000162>
[pid  1751] 22:03:51 epoll_create(1)    = 4 <0.000238>
[pid  1751] 22:03:51 epoll_wait(4, NULL, 0, 0) = -1 EINVAL (Invalid argument) <0.000166>
[pid  1751] 22:03:51 epoll_create(1)    = 5 <0.000231>
[pid  1751] 22:03:51 epoll_wait(5, NULL, 0, 0) = -1 EINVAL (Invalid argument) <0.000163>
[pid  1751] 22:03:51 epoll_create(1)    = 6 <0.000625>
[pid  1751] 22:03:51 epoll_wait(6, NULL, 0, 0) = -1 EINVAL (Invalid argument) <0.000202>
[pid  1751] 22:03:51 epoll_create(1)    = 7 <0.000158>
[pid  1751] 22:03:51 epoll_wait(7, NULL, 0, 0) = -1 EINVAL (Invalid argument) <0.000375>
[pid  1751] 22:03:51 epoll_create(1)    = 8 <0.000150>
[pid  1751] 22:03:51 epoll_wait(8, NULL, 0, 0) = -1 EINVAL (Invalid argument) <0.000187>
[pid  1751] 22:03:51 epoll_create(1)    = 9 <0.000143>
[pid  1751] 22:03:51 epoll_wait(9, NULL, 0, 0) = -1 EINVAL (Invalid argument) <0.000129>
[pid  1751] 22:03:51 epoll_create(1)    = 10 <0.000210>
[pid  1751] 22:03:51 epoll_wait(10, NULL, 0, 0) = -1 EINVAL (Invalid argument) <0.000217>
[pid  1751] 22:03:51 epoll_create(1)    = 11 <0.000163>
[pid  1751] 22:03:51 epoll_wait(11, NULL, 0, 0) = -1 EINVAL (Invalid argument) <0.000197>
[pid  1751] 22:03:51 epoll_create(1)    = 12 <0.000102>
[pid  1751] 22:03:51 epoll_wait(12, NULL, 0, 0) = -1 EINVAL (Invalid argument) <0.000169>
[pid  1751] 22:03:51 madvise(0x7fce5ff31000, 8368128, MADV_DONTNEED) = 0 <0.000105>
[pid  1751] 22:03:51 exit(0)            = ?
[pid  1750] 22:03:51 <... futex resumed> ) = 0 <0.015823>
[pid  1750] 22:03:51 exit_group(0)      = ?
[pid  1751] 22:03:51 +++ exited with 0 +++
22:03:51 +++ exited with 0 +++

The futex here is the pthread_join.

+1
toffaletti on Mar 11, 2018
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