From: Oleg Nesterov <oleg@redhat.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Kees Cook <keescook@chromium.org>, Will Drewry <wad@chromium.org>,
X86 ML <x86@kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Linux MIPS Mailing List <linux-mips@linux-mips.org>,
linux-arch <linux-arch@vger.kernel.org>,
LSM List <linux-security-module@vger.kernel.org>,
Alexei Starovoitov <ast@plumgrid.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v4 2/5] x86,entry: Only call user_exit if TIF_NOHZ
Date: Thu, 31 Jul 2014 18:58:04 +0200 [thread overview]
Message-ID: <20140731165804.GB16800@redhat.com> (raw)
In-Reply-To: <20140731165423.GA16800@redhat.com>
On 07/31, Oleg Nesterov wrote:
>
> On 07/31, Frederic Weisbecker wrote:
> >
> > On Thu, Jul 31, 2014 at 06:42:46PM +0200, Oleg Nesterov wrote:
> > >
> > > And if we change this, then the code above becomes racy. The state of
> > > TIF_XYZ can be changed right after the check. OK, it is racy anyway ;)
> > > but still this adds more confusion.
> >
> > No because all running tasks have this flag set when context tracking is
> > enabled. And context tracking can't be disabled on runtime.
>
> Yes, yes, please note that I said "if we change this".
And "it is racy anyway" connects to the problems we discuss in another
thread.
Oleg.
WARNING: multiple messages have this Message-ID (diff)
From: oleg@redhat.com (Oleg Nesterov)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v4 2/5] x86,entry: Only call user_exit if TIF_NOHZ
Date: Thu, 31 Jul 2014 18:58:04 +0200 [thread overview]
Message-ID: <20140731165804.GB16800@redhat.com> (raw)
In-Reply-To: <20140731165423.GA16800@redhat.com>
On 07/31, Oleg Nesterov wrote:
>
> On 07/31, Frederic Weisbecker wrote:
> >
> > On Thu, Jul 31, 2014 at 06:42:46PM +0200, Oleg Nesterov wrote:
> > >
> > > And if we change this, then the code above becomes racy. The state of
> > > TIF_XYZ can be changed right after the check. OK, it is racy anyway ;)
> > > but still this adds more confusion.
> >
> > No because all running tasks have this flag set when context tracking is
> > enabled. And context tracking can't be disabled on runtime.
>
> Yes, yes, please note that I said "if we change this".
And "it is racy anyway" connects to the problems we discuss in another
thread.
Oleg.
next prev parent reply other threads:[~2014-07-31 16:58 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-29 3:38 [PATCH v4 0/5] x86: two-phase syscall tracing and seccomp fastpath Andy Lutomirski
2014-07-29 3:38 ` Andy Lutomirski
2014-07-29 3:38 ` [PATCH v4 1/5] x86,x32,audit: Fix x32's AUDIT_ARCH wrt audit Andy Lutomirski
2014-07-29 3:38 ` Andy Lutomirski
2014-07-29 3:38 ` [PATCH v4 2/5] x86,entry: Only call user_exit if TIF_NOHZ Andy Lutomirski
2014-07-29 3:38 ` Andy Lutomirski
2014-07-29 19:32 ` Oleg Nesterov
2014-07-29 19:32 ` Oleg Nesterov
2014-07-30 16:43 ` Frederic Weisbecker
2014-07-30 16:43 ` Frederic Weisbecker
2014-07-30 17:23 ` Andy Lutomirski
2014-07-30 17:23 ` Andy Lutomirski
2014-07-31 15:16 ` Frederic Weisbecker
2014-07-31 15:16 ` Frederic Weisbecker
2014-07-31 16:42 ` Oleg Nesterov
2014-07-31 16:42 ` Oleg Nesterov
2014-07-31 16:49 ` Frederic Weisbecker
2014-07-31 16:49 ` Frederic Weisbecker
2014-07-31 16:54 ` Oleg Nesterov
2014-07-31 16:54 ` Oleg Nesterov
2014-07-31 16:58 ` Oleg Nesterov [this message]
2014-07-31 16:58 ` Oleg Nesterov
2014-07-31 17:17 ` Frederic Weisbecker
2014-07-31 17:17 ` Frederic Weisbecker
2014-07-29 3:38 ` [PATCH v4 3/5] x86: Split syscall_trace_enter into two phases Andy Lutomirski
2014-07-29 3:38 ` Andy Lutomirski
2014-07-29 19:25 ` Oleg Nesterov
2014-07-29 19:25 ` Oleg Nesterov
2014-07-29 3:38 ` [PATCH v4 4/5] x86_64,entry: Treat regs->ax the same in fastpath and slowpath syscalls Andy Lutomirski
2014-07-29 3:38 ` [PATCH v4 4/5] x86_64, entry: " Andy Lutomirski
2014-07-29 3:38 ` [PATCH v4 5/5] x86_64,entry: Use split-phase syscall_trace_enter for 64-bit syscalls Andy Lutomirski
2014-07-29 3:38 ` [PATCH v4 5/5] x86_64, entry: " Andy Lutomirski
2014-07-29 19:20 ` [PATCH v4 0/5] x86: two-phase syscall tracing and seccomp fastpath Oleg Nesterov
2014-07-29 19:20 ` Oleg Nesterov
2014-07-29 20:54 ` Andy Lutomirski
2014-07-29 20:54 ` Andy Lutomirski
2014-07-29 23:30 ` Andy Lutomirski
2014-07-29 23:30 ` Andy Lutomirski
2014-07-30 15:32 ` Oleg Nesterov
2014-07-30 15:32 ` Oleg Nesterov
2014-07-30 16:59 ` Frederic Weisbecker
2014-07-30 16:59 ` Frederic Weisbecker
2014-07-30 17:25 ` Andy Lutomirski
2014-07-30 17:25 ` Andy Lutomirski
2014-07-31 16:56 ` H. Peter Anvin
2014-07-31 16:56 ` H. Peter Anvin
2014-07-31 17:20 ` Frederic Weisbecker
2014-07-31 17:20 ` Frederic Weisbecker
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