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Commit a24864a1 authored by Lepton Wu's avatar Lepton Wu Committed by Linus Torvalds
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uml: definitively kill subprocesses on panic 



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: default avatarLepton Wu <ytht.net@gmail.com>
Signed-off-by: default avatarJeff Dike <jdike@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cb8fa61c

arch/um/os-Linux/skas/process.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -177,7 +177,7 @@ static int userspace_tramp(void *stack) 




	ptrace(PTRACE_TRACEME, 0, 0, 0);

	ptrace(PTRACE_TRACEME, 0, 0, 0);





	init_new_thread_signals();

	signal(SIGTERM, SIG_DFL);

	err = set_interval();

	err = set_interval();

	if (err)

	if (err)

		panic("userspace_tramp - setting timer failed, errno = %d\n",

		panic("userspace_tramp - setting timer failed, errno = %d\n",

arch/um/os-Linux/util.c

+38 −0
Original line number Original line Diff line number Diff line
@@ -105,6 +105,44 @@ int setjmp_wrapper(void (*proc)(void *, void *), ...) 




void os_dump_core(void)

void os_dump_core(void)

{

{

	int pid;



	signal(SIGSEGV, SIG_DFL);

	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();

	abort();

}
 
}