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authorOleg Nesterov <oleg@redhat.com>2014-06-05 03:12:19 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-05 03:54:21 +0400
commit34a1b7236ad6113883f6c448d1da854cad60265e (patch)
treeb49f5cb08f355563a679766f67cf318d427737b3
parent7b0b73d76651e5f88c88b76efa18d719f832bf6f (diff)
downloadlinux-34a1b7236ad6113883f6c448d1da854cad60265e.tar.xz
kthreads: kill CLONE_KERNEL, change kernel_thread(kernel_init) to avoid CLONE_SIGHAND
1. Remove CLONE_KERNEL, it has no users and it is dangerous. The (old) comment says "List of flags we want to share for kernel threads" but this is not true, we do not want to share ->sighand by default. This flag can only be used if the caller is sure that both parent/child will never play with signals (say, allow_signal/etc). 2. Change rest_init() to clone kernel_init() without CLONE_SIGHAND. In this case CLONE_SIGHAND does not really hurt, and it looks like optimization because copy_sighand() can avoid kmem_cache_alloc(). But in fact this only adds the minor pessimization. kernel_init() is going to exec the init process, and de_thread() will need to unshare ->sighand and do kmem_cache_alloc(sighand_cachep) anyway, but it needs to do more work and take tasklist_lock and siglock. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/sched.h6
-rw-r--r--init/main.c2
2 files changed, 1 insertions, 7 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 611676fd4c2c..8fcd0e6098d9 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -137,12 +137,6 @@ struct filename;
#define VMACACHE_MASK (VMACACHE_SIZE - 1)
/*
- * List of flags we want to share for kernel threads,
- * if only because they are not used by them anyway.
- */
-#define CLONE_KERNEL (CLONE_FS | CLONE_FILES | CLONE_SIGHAND)
-
-/*
* These are the constant used to fake the fixed-point load-average
* counting. Some notes:
* - 11 bit fractions expand to 22 bits by the multiplies: this gives
diff --git a/init/main.c b/init/main.c
index 8ac3833f2bdf..4de815c0309a 100644
--- a/init/main.c
+++ b/init/main.c
@@ -380,7 +380,7 @@ static noinline void __init_refok rest_init(void)
* the init task will end up wanting to create kthreads, which, if
* we schedule it before we create kthreadd, will OOPS.
*/
- kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
+ kernel_thread(kernel_init, NULL, CLONE_FS);
numa_default_policy();
pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
rcu_read_lock();