Re: INFO: rcu detected stall in io_playback_transfer

[Tetsuo Handa]

I manually simplified the reproducer.

It is quite strange that removing unshare() hides this lockup bug.
Also, explicitly closing by "close()" hides this lockup bug.
Triggering "fput() from do_exit()" from "different namespace"
somehow affects this lockup bug?

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#define _GNU_SOURCE
#include <fcntl.h>
#include <sched.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/soundcard.h>

int main(int argc, char *argv[])
{
	const int fd = open("/dev/dsp1", O_RDWR);
	int frag = (0 << 16) | 0;
	char buf[48] = { };
	unshare(CLONE_NEWNS);
	ioctl(fd, SNDCTL_DSP_SETFRAGMENT, &frag);
	write(fd, buf, sizeof(buf));
	return 0;
}
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