Messages in this thread | | | Date | Fri, 10 Sep 2004 09:39:27 -0700 | From | "H. J. Lu" <> | Subject | Re: Hanging process on SMP machines? |
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On Fri, Sep 10, 2004 at 12:45:49AM -0700, Andrew Morton wrote: > "H. J. Lu" <hjl@lucon.org> wrote: > > > > I notice that a process may hang on SMP machines at random: > > > > http://bugzilla.kernel.org/show_bug.cgi?id=3332 > > > > I can reliably trigger it within 15 minutes under SMP kernel on P4 HT > > and 4-way ia64 machines. Has anyone else seen it? > > It's easy to reproduce on 2-way x86, however it doesn't look like a kernel > bug. > > > akpm 2503 0.0 0.2 3892 640 pts/0 S 00:34 0:00 | \_ make > akpm 2504 0.0 0.0 1368 192 pts/0 S 00:34 0:00 | \_ time expect test.exp > akpm 2505 0.0 0.5 4776 1276 pts/0 S 00:34 0:00 | \_ expect test.exp > akpm 4726 0.0 0.0 0 0 ? Z 00:35 0:00 | \_ [true] <defunct> > > process 4726 is sleeping at the end of do_exit(): > > > schedule(); <<- here > BUG(); > /* Avoid "noreturn function does return". */ > for (;;) ; > } > > So it has completely exitted and is waiting for someone to reap its exit > code and stack slot via wait4(). So what is its parent up to? > > > (gdb) thread 69 > [Switching to thread 69 (Thread 2505)]#0 0xc01653e9 in do_select (n=5, fds=0xcc8b5fa4, > timeout=0xcc8b5fa0) at fs/select.c:257 > 257 __timeout = schedule_timeout(__timeout); > (gdb) bt > #0 0xc01653e9 in do_select (n=5, fds=0xcc8b5fa4, timeout=0xcc8b5fa0) at fs/select.c:257 > #1 0xc016579c in sys_select (n=5, inp=0x804b444, outp=0x804b4c4, exp=0x804b544, tvp=0xbfffe1d0) > at fs/select.c:354 > #2 0xc0105e39 in sysenter_past_esp () at arch/i386/kernel/semaphore.c:177 > > The parent is sleeping in select() rather than wait()ing for children. >
I don't think SIGCHLD is blocked. Shouldn't SIGCHLD interrupt select? UP kernel doesn't have this problem.
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