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uml: definitively kill subprocesses on panic

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In a stock 2.6.22.6 kernel, poweroff a user mode linux guest (2.6.22.6 running
in skas0 mode) will halt the host linux.  I think the reason is the kernel
thread abort because of a bug.  Then the sys_reboot in process of user mode
linux guest is not trapped by the user mode linux kernel and is executed by
host.  I think it is better to make sure all of our children process to quit
when user mode linux kernel abort.

[ jdike - the kernel process needs to ignore SIGTERM, plus the waitpid/kill
loop is needed to make sure that all of our children are dead before the
kernel exits ]

Signed-off-by: Lepton Wu <ytht.net@gmail.com>
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Lepton Wu 2007-10-16 01:27:35 -07:00 committed by Linus Torvalds
parent cb8fa61c2b
commit a24864a1d5
2 changed files with 39 additions and 1 deletions
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2
arch/um/os-Linux/skas/process.c
View file

@ -177,7 +177,7 @@ static int userspace_tramp(void *stack)
ptrace(PTRACE_TRACEME, 0, 0, 0);
init_new_thread_signals();
signal(SIGTERM, SIG_DFL);
err = set_interval();
if (err)
panic("userspace_tramp - setting timer failed, errno = %d\n",

38
arch/um/os-Linux/util.c
View file

@ -105,6 +105,44 @@ int setjmp_wrapper(void (*proc)(void *, void *), ...)
void os_dump_core(void)
{
int pid;
signal(SIGSEGV, SIG_DFL);
/*
* We are about to SIGTERM this entire process group to ensure that
* nothing is around to run after the kernel exits. The
* kernel wants to abort, not die through SIGTERM, so we
* ignore it here.
*/
signal(SIGTERM, SIG_IGN);
kill(0, SIGTERM);
/*
* Most of the other processes associated with this UML are
* likely sTopped, so give them a SIGCONT so they see the
* SIGTERM.
*/
kill(0, SIGCONT);
/*
* Now, having sent signals to everyone but us, make sure they
* die by ptrace. Processes can survive what's been done to
* them so far - the mechanism I understand is receiving a
* SIGSEGV and segfaulting immediately upon return. There is
* always a SIGSEGV pending, and (I'm guessing) signals are
* processed in numeric order so the SIGTERM (signal 15 vs
* SIGSEGV being signal 11) is never handled.
*
* Run a waitpid loop until we get some kind of error.
* Hopefully, it's ECHILD, but there's not a lot we can do if
* it's something else. Tell os_kill_ptraced_process not to
* wait for the child to report its death because there's
* nothing reasonable to do if that fails.
*/
while ((pid = waitpid(-1, NULL, WNOHANG)) > 0)
os_kill_ptraced_process(pid, 0);
abort();
}