d25c83c660
The comments in kernel/kthread.c create a feeling that only SIGKILL is
able to terminate the creation of kernel kthreads by
kthread_create()/_on_node()/_on_cpu() APIs.
In reality, wait_for_completion_killable() might be killed by any fatal
signal that does not have a custom handler:
(!siginmask(signr, SIG_KERNEL_IGNORE_MASK|SIG_KERNEL_STOP_MASK) && \
(t)->sighand->action[(signr)-1].sa.sa_handler == SIG_DFL)
static inline void signal_wake_up(struct task_struct *t, bool resume)
{
signal_wake_up_state(t, resume ? TASK_WAKEKILL : 0);
}
static void complete_signal(int sig, struct task_struct *p, enum pid_type type)
{
[...]
/*
* Found a killable thread. If the signal will be fatal,
* then start taking the whole group down immediately.
*/
if (sig_fatal(p, sig) ...) {
if (!sig_kernel_coredump(sig)) {
[...]
do {
task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
sigaddset(&t->pending.signal, SIGKILL);
signal_wake_up(t, 1);
} while_each_thread(p, t);
return;
}
}
}
Update the comments in kernel/kthread.c to make this more obvious.
The motivation for this change was debugging why a module initialization
failed. The module was being loaded from initrd. It "magically" failed
when systemd was switching to the real root. The clean up operations sent
SIGTERM to various pending processed that were started from initrd.
Link: https://lkml.kernel.org/r/20220315102444.2380-1-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Kees Cook <keescook@chromium.org>
Cc: Marco Elver <elver@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.