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* [PATCH] x86: do_signal: simplify the TS_RESTORE_SIGMASK logic
@ 2011-07-10 18:22 Oleg Nesterov
  2011-07-10 21:08 ` Al Viro
                   ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Oleg Nesterov @ 2011-07-10 18:22 UTC (permalink / raw)
  To: Andrew Morton; +Cc: David Howells, David Woodhouse, Ingo Molnar, linux-kernel

1. do_signal() looks at TS_RESTORE_SIGMASK and calculates the
   mask which should be stored in the signal frame, then it
   passes "oldset" to the callees, down to setup_rt_frame().

   This is ugly, setup_rt_frame() can do this itself and nobody
   else needs this sigset_t. Move this code into setup_rt_frame.

2. do_signal() also clears TS_RESTORE_SIGMASK if handle_signal()
   succeeds.

   We can move this to setup_rt_frame() as well, this avoids the
   unnecessary checks and makes the logic more clear.

3. use set_current_blocked() instead of sigprocmask(SIG_SETMASK),
   sigprocmask() should be avoided.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---

 arch/x86/kernel/signal.c |   29 ++++++++++-------------------
 1 file changed, 10 insertions(+), 19 deletions(-)

--- ptrace/arch/x86/kernel/signal.c~2_restore_sigmask	2011-07-10 18:06:30.000000000 +0200
+++ ptrace/arch/x86/kernel/signal.c	2011-07-10 19:45:21.000000000 +0200
@@ -653,11 +653,15 @@ int ia32_setup_frame(int sig, struct k_s
 
 static int
 setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
-	       sigset_t *set, struct pt_regs *regs)
+		struct pt_regs *regs)
 {
 	int usig = signr_convert(sig);
+	sigset_t *set = &current->blocked;
 	int ret;
 
+	if (current_thread_info()->status & TS_RESTORE_SIGMASK)
+		set = &current->saved_sigmask;
+
 	/* Set up the stack frame */
 	if (is_ia32) {
 		if (ka->sa.sa_flags & SA_SIGINFO)
@@ -672,12 +676,13 @@ setup_rt_frame(int sig, struct k_sigacti
 		return -EFAULT;
 	}
 
+	current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
 	return ret;
 }
 
 static int
 handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
-	      sigset_t *oldset, struct pt_regs *regs)
+		struct pt_regs *regs)
 {
 	sigset_t blocked;
 	int ret;
@@ -712,7 +717,7 @@ handle_signal(unsigned long sig, siginfo
 	    likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
 		regs->flags &= ~X86_EFLAGS_TF;
 
-	ret = setup_rt_frame(sig, ka, info, oldset, regs);
+	ret = setup_rt_frame(sig, ka, info, regs);
 
 	if (ret)
 		return ret;
@@ -758,7 +763,6 @@ static void do_signal(struct pt_regs *re
 	struct k_sigaction ka;
 	siginfo_t info;
 	int signr;
-	sigset_t *oldset;
 
 	/*
 	 * We want the common case to go fast, which is why we may in certain
@@ -770,23 +774,10 @@ static void do_signal(struct pt_regs *re
 	if (!user_mode(regs))
 		return;
 
-	if (current_thread_info()->status & TS_RESTORE_SIGMASK)
-		oldset = &current->saved_sigmask;
-	else
-		oldset = &current->blocked;
-
 	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 	if (signr > 0) {
 		/* Whee! Actually deliver the signal.  */
-		if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
-			/*
-			 * A signal was successfully delivered; the saved
-			 * sigmask will have been stored in the signal frame,
-			 * and will be restored by sigreturn, so we can simply
-			 * clear the TS_RESTORE_SIGMASK flag.
-			 */
-			current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
-		}
+		handle_signal(signr, &info, &ka, regs);
 		return;
 	}
 
@@ -814,7 +805,7 @@ static void do_signal(struct pt_regs *re
 	 */
 	if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
 		current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
-		sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
+		set_current_blocked(&current->saved_sigmask);
 	}
 }
 


^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] x86: do_signal: simplify the TS_RESTORE_SIGMASK logic
  2011-07-10 18:22 [PATCH] x86: do_signal: simplify the TS_RESTORE_SIGMASK logic Oleg Nesterov
@ 2011-07-10 21:08 ` Al Viro
  2011-07-11 11:39   ` Oleg Nesterov
  2011-07-13  9:25 ` Matt Fleming
  2011-07-15  5:47 ` [tip:x86/signal] x86, do_signal: Simplify " tip-bot for Oleg Nesterov
  2 siblings, 1 reply; 6+ messages in thread
From: Al Viro @ 2011-07-10 21:08 UTC (permalink / raw)
  To: Oleg Nesterov
  Cc: Andrew Morton, David Howells, David Woodhouse, Ingo Molnar,
	linux-kernel

On Sun, Jul 10, 2011 at 08:22:03PM +0200, Oleg Nesterov wrote:

> 2. do_signal() also clears TS_RESTORE_SIGMASK if handle_signal()
>    succeeds.
> 
>    We can move this to setup_rt_frame() as well, this avoids the
>    unnecessary checks and makes the logic more clear.


> +	current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
>  	return ret;

This is broken.  If setup_rt_frame() fails, you don't want to do that.

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] x86: do_signal: simplify the TS_RESTORE_SIGMASK logic
  2011-07-10 21:08 ` Al Viro
@ 2011-07-11 11:39   ` Oleg Nesterov
  0 siblings, 0 replies; 6+ messages in thread
From: Oleg Nesterov @ 2011-07-11 11:39 UTC (permalink / raw)
  To: Al Viro
  Cc: Andrew Morton, David Howells, David Woodhouse, Ingo Molnar,
	linux-kernel

On 07/10, Al Viro wrote:
>
> On Sun, Jul 10, 2011 at 08:22:03PM +0200, Oleg Nesterov wrote:
>
> > 2. do_signal() also clears TS_RESTORE_SIGMASK if handle_signal()
> >    succeeds.
> >
> >    We can move this to setup_rt_frame() as well, this avoids the
> >    unnecessary checks and makes the logic more clear.
>
>
> > +	current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
> >  	return ret;
>
> This is broken.

You know, I was also going to change this "return ret", "return 0"
looks more clear to me. But then I should have renamed "ret", and
I decided to leave  it alone.

> If setup_rt_frame() fails, you don't want to do that.

Sure. Please look at the code, it does

	if (ret) {
		force_sigsegv(sig, current);
		return -EFAULT;
	}

	current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
	return ret;

We clear TS_RESTORE_SIGMASK only if we return 0.

Oleg.


^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] x86: do_signal: simplify the TS_RESTORE_SIGMASK logic
  2011-07-10 18:22 [PATCH] x86: do_signal: simplify the TS_RESTORE_SIGMASK logic Oleg Nesterov
  2011-07-10 21:08 ` Al Viro
@ 2011-07-13  9:25 ` Matt Fleming
  2011-07-13 15:23   ` Oleg Nesterov
  2011-07-15  5:47 ` [tip:x86/signal] x86, do_signal: Simplify " tip-bot for Oleg Nesterov
  2 siblings, 1 reply; 6+ messages in thread
From: Matt Fleming @ 2011-07-13  9:25 UTC (permalink / raw)
  To: Oleg Nesterov
  Cc: Andrew Morton, David Howells, David Woodhouse, Ingo Molnar,
	linux-kernel

On Sun, 10 Jul 2011 20:22:03 +0200
Oleg Nesterov <oleg@redhat.com> wrote:

> 1. do_signal() looks at TS_RESTORE_SIGMASK and calculates the
>    mask which should be stored in the signal frame, then it
>    passes "oldset" to the callees, down to setup_rt_frame().
> 
>    This is ugly, setup_rt_frame() can do this itself and nobody
>    else needs this sigset_t. Move this code into setup_rt_frame.
> 
> 2. do_signal() also clears TS_RESTORE_SIGMASK if handle_signal()
>    succeeds.
> 
>    We can move this to setup_rt_frame() as well, this avoids the
>    unnecessary checks and makes the logic more clear.
> 
> 3. use set_current_blocked() instead of sigprocmask(SIG_SETMASK),
>    sigprocmask() should be avoided.

Could you please mention commit e6fa16ab "signal: sigprocmask() should
do retarget_shared_pending()", since it's not immediately obvious in
this changelog why sigprocmask() should be avoided.

> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

FWIW,

Reviewed-by: Matt Fleming <matt.fleming@linux.intel.com>

-- 
Matt Fleming, Intel Open Source Technology Center

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] x86: do_signal: simplify the TS_RESTORE_SIGMASK logic
  2011-07-13  9:25 ` Matt Fleming
@ 2011-07-13 15:23   ` Oleg Nesterov
  0 siblings, 0 replies; 6+ messages in thread
From: Oleg Nesterov @ 2011-07-13 15:23 UTC (permalink / raw)
  To: Matt Fleming
  Cc: Andrew Morton, David Howells, David Woodhouse, Ingo Molnar,
	linux-kernel

On 07/13, Matt Fleming wrote:
>
> On Sun, 10 Jul 2011 20:22:03 +0200
> Oleg Nesterov <oleg@redhat.com> wrote:
>
> > 1. do_signal() looks at TS_RESTORE_SIGMASK and calculates the
> >    mask which should be stored in the signal frame, then it
> >    passes "oldset" to the callees, down to setup_rt_frame().
> >
> >    This is ugly, setup_rt_frame() can do this itself and nobody
> >    else needs this sigset_t. Move this code into setup_rt_frame.
> >
> > 2. do_signal() also clears TS_RESTORE_SIGMASK if handle_signal()
> >    succeeds.
> >
> >    We can move this to setup_rt_frame() as well, this avoids the
> >    unnecessary checks and makes the logic more clear.
> >
> > 3. use set_current_blocked() instead of sigprocmask(SIG_SETMASK),
> >    sigprocmask() should be avoided.
>
> Could you please mention commit e6fa16ab "signal: sigprocmask() should
> do retarget_shared_pending()", since it's not immediately obvious in
> this changelog why sigprocmask() should be avoided.

Well, sigprocmask(SIG_SETMASK) is fine from the correctness pov,
it calls set_current_blocked().

sigprocmask() should be avoided because it is strange interface.
It has numeruos callers, but in fact almost all of them could use
set_current_blocked() (ignoring sys_rt_sigprocmask).

Linus suggested to simply kill sigprocmask(). I am not sure, but
at least it shouldn't be abused and its last argument is confusing.

> Reviewed-by: Matt Fleming <matt.fleming@linux.intel.com>

Thanks for looking!

Oleg.


^ permalink raw reply	[flat|nested] 6+ messages in thread
* [tip:x86/signal] x86, do_signal: Simplify the TS_RESTORE_SIGMASK logic
  2011-07-10 18:22 [PATCH] x86: do_signal: simplify the TS_RESTORE_SIGMASK logic Oleg Nesterov
  2011-07-10 21:08 ` Al Viro
  2011-07-13  9:25 ` Matt Fleming
@ 2011-07-15  5:47 ` tip-bot for Oleg Nesterov
  2 siblings, 0 replies; 6+ messages in thread
From: tip-bot for Oleg Nesterov @ 2011-07-15  5:47 UTC (permalink / raw)
  To: linux-tip-commits; +Cc: linux-kernel, hpa, mingo, oleg, tglx, hpa

Commit-ID:  9b429620740945363b746414e8b9a84b8119914c
Gitweb:     http://git.kernel.org/tip/9b429620740945363b746414e8b9a84b8119914c
Author:     Oleg Nesterov <oleg@redhat.com>
AuthorDate: Sun, 10 Jul 2011 20:22:03 +0200
Committer:  H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Thu, 14 Jul 2011 21:22:11 -0700

x86, do_signal: Simplify the TS_RESTORE_SIGMASK logic

1. do_signal() looks at TS_RESTORE_SIGMASK and calculates the
   mask which should be stored in the signal frame, then it
   passes "oldset" to the callees, down to setup_rt_frame().

   This is ugly, setup_rt_frame() can do this itself and nobody
   else needs this sigset_t. Move this code into setup_rt_frame.

2. do_signal() also clears TS_RESTORE_SIGMASK if handle_signal()
   succeeds.

   We can move this to setup_rt_frame() as well, this avoids the
   unnecessary checks and makes the logic more clear.

3. use set_current_blocked() instead of sigprocmask(SIG_SETMASK),
   sigprocmask() should be avoided.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Link: http://lkml.kernel.org/r/20110710182203.GA27979@redhat.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
 arch/x86/kernel/signal.c |   29 ++++++++++-------------------
 1 files changed, 10 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index bf9345d..8c55f97 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -651,11 +651,15 @@ int ia32_setup_frame(int sig, struct k_sigaction *ka,
 
 static int
 setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
-	       sigset_t *set, struct pt_regs *regs)
+		struct pt_regs *regs)
 {
 	int usig = signr_convert(sig);
+	sigset_t *set = &current->blocked;
 	int ret;
 
+	if (current_thread_info()->status & TS_RESTORE_SIGMASK)
+		set = &current->saved_sigmask;
+
 	/* Set up the stack frame */
 	if (is_ia32) {
 		if (ka->sa.sa_flags & SA_SIGINFO)
@@ -670,12 +674,13 @@ setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 		return -EFAULT;
 	}
 
+	current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
 	return ret;
 }
 
 static int
 handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
-	      sigset_t *oldset, struct pt_regs *regs)
+		struct pt_regs *regs)
 {
 	sigset_t blocked;
 	int ret;
@@ -710,7 +715,7 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
 	    likely(test_and_clear_thread_flag(TIF_FORCED_TF)))
 		regs->flags &= ~X86_EFLAGS_TF;
 
-	ret = setup_rt_frame(sig, ka, info, oldset, regs);
+	ret = setup_rt_frame(sig, ka, info, regs);
 
 	if (ret)
 		return ret;
@@ -765,7 +770,6 @@ static void do_signal(struct pt_regs *regs)
 	struct k_sigaction ka;
 	siginfo_t info;
 	int signr;
-	sigset_t *oldset;
 
 	/*
 	 * We want the common case to go fast, which is why we may in certain
@@ -777,23 +781,10 @@ static void do_signal(struct pt_regs *regs)
 	if (!user_mode(regs))
 		return;
 
-	if (current_thread_info()->status & TS_RESTORE_SIGMASK)
-		oldset = &current->saved_sigmask;
-	else
-		oldset = &current->blocked;
-
 	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 	if (signr > 0) {
 		/* Whee! Actually deliver the signal.  */
-		if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
-			/*
-			 * A signal was successfully delivered; the saved
-			 * sigmask will have been stored in the signal frame,
-			 * and will be restored by sigreturn, so we can simply
-			 * clear the TS_RESTORE_SIGMASK flag.
-			 */
-			current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
-		}
+		handle_signal(signr, &info, &ka, regs);
 		return;
 	}
 
@@ -821,7 +812,7 @@ static void do_signal(struct pt_regs *regs)
 	 */
 	if (current_thread_info()->status & TS_RESTORE_SIGMASK) {
 		current_thread_info()->status &= ~TS_RESTORE_SIGMASK;
-		sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
+		set_current_blocked(&current->saved_sigmask);
 	}
 }
 

^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2011-07-15  5:47 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2011-07-10 18:22 [PATCH] x86: do_signal: simplify the TS_RESTORE_SIGMASK logic Oleg Nesterov
2011-07-10 21:08 ` Al Viro
2011-07-11 11:39   ` Oleg Nesterov
2011-07-13  9:25 ` Matt Fleming
2011-07-13 15:23   ` Oleg Nesterov
2011-07-15  5:47 ` [tip:x86/signal] x86, do_signal: Simplify " tip-bot for Oleg Nesterov

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