Hi Christian,
Thanks for the report.
On Sat, 25 Jul 2026 15:12:54 +0200
Christian Franke wrote:
> After 524d75ff ("Cygwin: open: Unlock fdtab before open_with_arch()"),
> CI workflow shows that 'stress-ng --procfs ...' now hangs.
>
> Testcase:
>
> $ uname -r # not with 3.7.0-0.567.g161e3cb999fb.x86_64
> 3.7.0-0.569.g524d75ff7398.x86_64
>
> $ cat proc-self-fd.c
> #include <errno.h>
> #include <fcntl.h>
> #include <pthread.h>
> #include <stdio.h>
> #include <unistd.h>
>
> static void * threadfunc(void * arg)
> {
> (void)arg;
> for (int i = 0; i < 100000; i++) {
> char path[32];
> snprintf(path, sizeof(path), "/proc/self/fd/%d", i % 10);
> int fd = open(path, O_RDONLY);
> if (fd < 0) {
> printf("%p#%06d: %s: errno=%d\n", pthread_self(), i, path, errno);
> continue;
> }
> printf("%p#%06d: %s: fd=%d\n", pthread_self(), i, path, fd);
> close(fd);
> }
> return NULL;
> }
>
> int main()
> {
> pthread_t t = NULL;
> int ret = pthread_create(&t, NULL, threadfunc, NULL);
> if (ret)
> return 1;
> threadfunc(NULL);
> ret = pthread_join(t, NULL);
> printf("pthread_join(%p, .)=%d\n", t, ret);
> if (ret)
> return 1;
> return 0;
> }
>
> $ gcc -o proc-self-fd proc-self-fd.c
>
> $ ./proc-self-fd
> ...
> 0xa00000500#001908: /proc/self/fd/8: errno=2
> 0xa00000010#001900: /proc/self/fd/0: fd=3
> 0xa00000500#001909: /proc/self/fd/9: errno=2
> 0xa00000010#001901: /proc/self/fd/1: errno=14<== EFAULT
> [hangs, kill -9 does not work]
>
> $ strace -o trace.log ./proc-self-fd
> [taskkill /f /im proc-self-fd.exe in other window]
>
> $ less trace.log
> ...
> 25 21725 [main] proc-self-fd 14876 fhandler_pty_slave::open_setup:
> /dev/pty1 opened, usecount 3
> 61 21786 [main] proc-self-fd 14876 build_fh_pc: found an archetype
> for (null)(136/1) io_handle 0x200
> 66 21852 [main] proc-self-fd 14876 build_fh_pc: fh 0x800008E40,
> dev 00880001
> 71 21923 [main] proc-self-fd 14876 fhandler_base::open_with_arch:
> line 471: /dev/pty1<0x8000086F0> usecount + 1 = 4
> --- Process 3968 (pid: 14876), exception c0000008 at 00007ff81682416a
> --- Process 3968 (pid: 14876), exception c0000008 at 00007ff81682416a
> ...
>
>
> "... found an archetype for (null) ..." <== Hmm...
Perhaps, this is due to the defects pointed out by Johannes.
https://cygwin.com/pipermail/cygwin-patches/2026q3/015227.html
--
Takashi Yano <[email protected]>
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