vfork makes processes uninterruptible [was Re: [PATCH -mm] swsusp: freeze user space processes first]

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > Can you produce userland testcase? If we have uninterruptible process for
> > days... that's a bug in kernel, suspend or not.
> 
> Sure, no problem.  [Pretty scary, no?]

Yes, pretty scary. It will also raise system load for 300 seconds
without any real load.

> The test code:
> 
> #include <sys/types.h>
> #include <unistd.h>
> 
> int main(int argc, char *argv[])
> {
> 	vfork();
> 	sleep(300);
> 
> 	return 0;
> }
> 
> The result:
> 
> rafael@albercik:~/programming/c> ./vfork_test &
> [1] 12288
> rafael@albercik:~/programming/c> ps l
> F   UID   PID  PPID PRI  NI    VSZ   RSS WCHAN  STAT TTY        TIME COMMAND
> 0   500  6937  6931  17   0  10048  2368 read_c Ss+  pts/1      0:00 /bin/bash
> 0   500 12139 12133  15   0  10052  2380 wait   Ss   pts/2      0:00 /bin/bash
> 0   500 12288 12139  15   0   2420   304 fork   D    pts/2      0:00 ./vfork_tes
> 1   500 12291 12288  18   0   2420   304 hrtime S    pts/2      0:00 ./vfork_tes
> 0   500 12372 12139  15   0   3596   820 -      R+   pts/2      0:00 ps l
> rafael@albercik:~/programming/c> kill 12288
> rafael@albercik:~/programming/c> ps l
> F   UID   PID  PPID PRI  NI    VSZ   RSS WCHAN  STAT TTY        TIME COMMAND
> 0   500  6937  6931  17   0  10048  2368 read_c Ss+  pts/1      0:00 /bin/bash
> 0   500 12139 12133  15   0  10052  2380 wait   Ss   pts/2      0:00 /bin/bash
> 0   500 12288 12139  15   0   2420   304 fork   D    pts/2      0:00 ./vfork_tes
> 1   500 12291 12288  18   0   2420   304 hrtime S    pts/2      0:00 ./vfork_tes
> 0   500 12380 12139  17   0   3600   820 -      R+   pts/2      0:00 ps l
> rafael@albercik:~/programming/c> kill -9 12288
> rafael@albercik:~/programming/c> ps l
> F   UID   PID  PPID PRI  NI    VSZ   RSS WCHAN  STAT TTY        TIME COMMAND
> 0   500  6937  6931  17   0  10048  2368 read_c Ss+  pts/1      0:00 /bin/bash
> 0   500 12139 12133  15   0  10052  2380 wait   Ss   pts/2      0:00 /bin/bash
> 0   500 12288 12139  15   0   2420   304 fork   D    pts/2      0:00 ./vfork_tes
> 1   500 12291 12288  18   0   2420   304 hrtime S    pts/2      0:00 ./vfork_tes
> 0   500 12387 12139  16   0   3596   816 -      R+   pts/2      0:00 ps l
> rafael@albercik:~/programming/c>
> 
> Greetings,
> Rafael

-- 
Web maintainer for suspend.sf.net (www.sf.net/projects/suspend) wanted...
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