The patch titled
change kernel threads to ignore signals instead of blocking them
has been removed from the -mm tree. Its filename was
change-kernel-threads-to-ignore-signals-instead-of-blocking-them.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: change kernel threads to ignore signals instead of blocking them
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Currently kernel threads use sigprocmask(SIG_BLOCK) to protect against
signals. This doesn't prevent the signal delivery, this only blocks
signal_wake_up(). Every "killall -33 kthreadd" means a "struct siginfo"
leak.
Change kthreadd_setup() to set all handlers to SIG_IGN instead of blocking
them (make a new helper ignore_signals() for that). If the kernel thread
needs some signal, it should use allow_signal() anyway, and in that case it
should not use CLONE_SIGHAND.
Note that we can't change daemonize() (should die!) in the same way,
because it can be used along with CLONE_SIGHAND. This means that
allow_signal() still should unblock the signal to work correctly with
daemonize()ed threads.
However, disallow_signal() doesn't block the signal any longer but ignores
it.
NOTE: with or without this patch the kernel threads are not protected from
handle_stop_signal(), this seems harmless, but not good.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sched.h | 1 +
kernel/exit.c | 2 +-
kernel/kthread.c | 17 +++--------------
kernel/signal.c | 10 ++++++++++
4 files changed, 15 insertions(+), 15 deletions(-)
diff -puN include/linux/sched.h~change-kernel-threads-to-ignore-signals-instead-of-blocking-them include/linux/sched.h
--- a/include/linux/sched.h~change-kernel-threads-to-ignore-signals-instead-of-blocking-them
+++ a/include/linux/sched.h
@@ -1318,6 +1318,7 @@ extern int in_egroup_p(gid_t);
extern void proc_caches_init(void);
extern void flush_signals(struct task_struct *);
+extern void ignore_signals(struct task_struct *);
extern void flush_signal_handlers(struct task_struct *, int force_default);
extern int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info);
diff -puN kernel/exit.c~change-kernel-threads-to-ignore-signals-instead-of-blocking-them kernel/exit.c
--- a/kernel/exit.c~change-kernel-threads-to-ignore-signals-instead-of-blocking-them
+++ a/kernel/exit.c
@@ -347,7 +347,7 @@ int disallow_signal(int sig)
return -EINVAL;
spin_lock_irq(¤t->sighand->siglock);
- sigaddset(¤t->blocked, sig);
+ current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
recalc_sigpending();
spin_unlock_irq(¤t->sighand->siglock);
return 0;
diff -puN kernel/kthread.c~change-kernel-threads-to-ignore-signals-instead-of-blocking-them kernel/kthread.c
--- a/kernel/kthread.c~change-kernel-threads-to-ignore-signals-instead-of-blocking-them
+++ a/kernel/kthread.c
@@ -215,24 +215,13 @@ EXPORT_SYMBOL(kthread_stop);
static __init void kthreadd_setup(void)
{
struct task_struct *tsk = current;
- struct k_sigaction sa;
- sigset_t blocked;
set_task_comm(tsk, "kthreadd");
- /* Block and flush all signals */
- sigfillset(&blocked);
- sigprocmask(SIG_BLOCK, &blocked, NULL);
- flush_signals(tsk);
-
- /* SIG_IGN makes children autoreap: see do_notify_parent(). */
- sa.sa.sa_handler = SIG_IGN;
- sa.sa.sa_flags = 0;
- siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
- do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
+ ignore_signals(tsk);
- set_user_nice(current, -5);
- set_cpus_allowed(current, CPU_MASK_ALL);
+ set_user_nice(tsk, -5);
+ set_cpus_allowed(tsk, CPU_MASK_ALL);
}
int kthreadd(void *unused)
diff -puN kernel/signal.c~change-kernel-threads-to-ignore-signals-instead-of-blocking-them kernel/signal.c
--- a/kernel/signal.c~change-kernel-threads-to-ignore-signals-instead-of-blocking-them
+++ a/kernel/signal.c
@@ -209,6 +209,16 @@ void flush_signals(struct task_struct *t
spin_unlock_irqrestore(&t->sighand->siglock, flags);
}
+void ignore_signals(struct task_struct *t)
+{
+ int i;
+
+ for (i = 0; i < _NSIG; ++i)
+ t->sighand->action[i].sa.sa_handler = SIG_IGN;
+
+ flush_signals(t);
+}
+
/*
* Flush all handlers for a task.
*/
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
freezer-read-pf_borrowed_mm-in-a-nonracy-way.patch
freezer-close-theoretical-race-between-refrigerator-and-thaw_tasks.patch
freezer-remove-pf_nofreeze-from-rcutorture-thread.patch
freezer-remove-pf_nofreeze-from-bluetooth-threads.patch
freezer-add-try_to_freeze-calls-to-all-kernel-threads.patch
freezer-fix-vfork-problem.patch
freezer-take-kernel_execve-into-consideration.patch
nlmclnt_recovery-dont-use-clone_sighand.patch
fix-kthread_create-vs-freezer-theoretical-race.patch
fix-pf_nofreeze-and-freezeable-race-2.patch
freezer-document-task_lock-in-thaw_process.patch
move-frozen_process-to-kernel-power-processc.patch
separate-freezer-from-pm-code-rev-2.patch
introduce-freezer-flags-rev-2.patch
libata-core-convert-to-use-cancel_rearming_delayed_work.patch
clone-flag-clone_parent_tidptr-leaves-invalid-results-in-memory.patch
getrusage-fill-ru_inblock-and-ru_oublock-fields-if-possible.patch
dont-init-pgrp-and-__session-in-init_signals.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
