Subject: + kthreads-kill-clone_kernel-change-kernel_threadkernel_init-to-avoid-clone_sighand.patch added to -mm tree
To: oleg@xxxxxxxxxx,fweisbec@xxxxxxxxx,mathieu.desnoyers@xxxxxxxxxxxx,mingo@xxxxxxxxxx,peterz@xxxxxxxxxxxxx,rostedt@xxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 16 Apr 2014 15:30:02 -0700
The patch titled
Subject: kthreads: kill CLONE_KERNEL, change kernel_thread(kernel_init) to avoid CLONE_SIGHAND
has been added to the -mm tree. Its filename is
kthreads-kill-clone_kernel-change-kernel_threadkernel_init-to-avoid-clone_sighand.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kthreads-kill-clone_kernel-change-kernel_threadkernel_init-to-avoid-clone_sighand.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kthreads-kill-clone_kernel-change-kernel_threadkernel_init-to-avoid-clone_sighand.patch
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From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sched.h | 6 ------
init/main.c | 2 +-
2 files changed, 1 insertion(+), 7 deletions(-)
diff -puN include/linux/sched.h~kthreads-kill-clone_kernel-change-kernel_threadkernel_init-to-avoid-clone_sighand include/linux/sched.h
--- a/include/linux/sched.h~kthreads-kill-clone_kernel-change-kernel_threadkernel_init-to-avoid-clone_sighand
+++ a/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 -puN init/main.c~kthreads-kill-clone_kernel-change-kernel_threadkernel_init-to-avoid-clone_sighand init/main.c
--- a/init/main.c~kthreads-kill-clone_kernel-change-kernel_threadkernel_init-to-avoid-clone_sighand
+++ a/init/main.c
@@ -380,7 +380,7 @@ static noinline void __init_refok rest_i
* 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();
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
mmvmacache-optimize-overflow-system-wide-flushing.patch
kthreads-kill-clone_kernel-change-kernel_threadkernel_init-to-avoid-clone_sighand.patch
signals-kill-sigfindinword.patch
signals-s-siginitset-sigemptyset-in-do_sigtimedwait.patch
signals-kill-rm_from_queue-change-prepare_signal-to-use-for_each_thread.patch
signals-rename-rm_from_queue_full-to-flush_sigqueue_mask.patch
signals-cleanup-the-usage-of-t-current-in-do_sigaction.patch
signals-mv-disallow_signal-from-schedh-exitc-to-signal.patch
signals-jffs2-fix-the-wrong-usage-of-disallow_signal.patch
signals-kill-the-obsolete-sigdelset-and-recalc_sigpending-in-allow_signal.patch
signals-disallow_signal-should-flush-the-potentially-pending-signal.patch
signals-introduce-kernel_sigaction.patch
signals-change-wait_for_helper-to-use-kernel_sigaction.patch
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