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Date: Thu, 19 Jun 2014 10:12:04 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Oleg Nesterov <oleg@...hat.com>
Subject: Re: [GIT PULL] tracing: Cleanups and fixes to syscall tracepoints
Linus,
Please do not pull this. I just found out that it can break other archs
as it uses TIF_SYSCALL_TRACEPOINT in generic code and not all archs
define it.
I'll work on a fix for this and send an update.
-- Steve
On Thu, 19 Jun 2014 09:59:08 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:
>
> Linus,
>
> This includes three patches from Oleg Nesterov. The first is a fix to a
> race condition that happens between enabling/disabling syscall tracepoints
> and new process creations (the check to go into the ptrace path for a process
> can be set when it shouldn't, or not set when it should). Not a major bug
> but one that should be fixed and even applied to stable.
>
> The other two patches are cleanup/fixes that are not that critical, but
> for an -rc1 release would be nice to have. They both deal with syscall
> tracepoints.
>
> I would have included these with my initial pull request, but as Oleg
> posted his last version as a reply to the bottom of the patch 1/3
> thread, I missed it.
>
> Please pull the latest trace-fixes-v3.16-rc1 tree, which can be found at:
>
>
> git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
> trace-fixes-v3.16-rc1
>
> Tag SHA1: b6890d3b54aa3ff1aa34afb6c7af367895b9f07a
> Head SHA1: 72fa1a896d8ef355e81270667803ceb16a3dd13f
>
>
> Oleg Nesterov (3):
> tracing: Fix syscall_*regfunc() vs copy_process() race
> tracing: Change syscall_*regfunc() to check PF_KTHREAD and use for_each_process_thread()
> tracing: syscall_regfunc() should not skip kernel threads
>
> ----
> include/trace/syscall.h | 15 +++++++++++++++
> kernel/fork.c | 2 ++
> kernel/tracepoint.c | 26 +++++++++++---------------
> 3 files changed, 28 insertions(+), 15 deletions(-)
> ---------------------------
> diff --git a/include/trace/syscall.h b/include/trace/syscall.h
> index fed853f3d7aa..291c2824fafb 100644
> --- a/include/trace/syscall.h
> +++ b/include/trace/syscall.h
> @@ -4,6 +4,7 @@
> #include <linux/tracepoint.h>
> #include <linux/unistd.h>
> #include <linux/ftrace_event.h>
> +#include <linux/thread_info.h>
>
> #include <asm/ptrace.h>
>
> @@ -32,4 +33,18 @@ struct syscall_metadata {
> struct ftrace_event_call *exit_event;
> };
>
> +#ifdef CONFIG_TRACEPOINTS
> +static inline void syscall_tracepoint_update(struct task_struct *p)
> +{
> + if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
> + set_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT);
> + else
> + clear_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT);
> +}
> +#else
> +static inline void syscall_tracepoint_update(struct task_struct *p)
> +{
> +}
> +#endif
> +
> #endif /* _TRACE_SYSCALL_H */
> diff --git a/kernel/fork.c b/kernel/fork.c
> index d2799d1fc952..6a13c46cd87d 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1487,7 +1487,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
>
> total_forks++;
> spin_unlock(¤t->sighand->siglock);
> + syscall_tracepoint_update(p);
> write_unlock_irq(&tasklist_lock);
> +
> proc_fork_connector(p);
> cgroup_post_fork(p);
> if (clone_flags & CLONE_THREAD)
> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> index 33cbd8c203f8..3490407dc7b7 100644
> --- a/kernel/tracepoint.c
> +++ b/kernel/tracepoint.c
> @@ -492,33 +492,29 @@ static int sys_tracepoint_refcount;
>
> void syscall_regfunc(void)
> {
> - unsigned long flags;
> - struct task_struct *g, *t;
> + struct task_struct *p, *t;
>
> if (!sys_tracepoint_refcount) {
> - read_lock_irqsave(&tasklist_lock, flags);
> - do_each_thread(g, t) {
> - /* Skip kernel threads. */
> - if (t->mm)
> - set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
> - } while_each_thread(g, t);
> - read_unlock_irqrestore(&tasklist_lock, flags);
> + read_lock(&tasklist_lock);
> + for_each_process_thread(p, t) {
> + set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
> + }
> + read_unlock(&tasklist_lock);
> }
> sys_tracepoint_refcount++;
> }
>
> void syscall_unregfunc(void)
> {
> - unsigned long flags;
> - struct task_struct *g, *t;
> + struct task_struct *p, *t;
>
> sys_tracepoint_refcount--;
> if (!sys_tracepoint_refcount) {
> - read_lock_irqsave(&tasklist_lock, flags);
> - do_each_thread(g, t) {
> + read_lock(&tasklist_lock);
> + for_each_process_thread(p, t) {
> clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
> - } while_each_thread(g, t);
> - read_unlock_irqrestore(&tasklist_lock, flags);
> + }
> + read_unlock(&tasklist_lock);
> }
> }
> #endif
--
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