linux-kernel - [PATCH 2/4] MN10300: Enable IRQs more in system call exit work path

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Date:	Tue, 28 May 2013 15:31:30 +0100
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...ux-foundation.com
Cc:	linux-am33-list@...hat.com, linux-kernel@...r.kernel.org,
	Ken Cox <jkc@...hat.com>
Subject: [PATCH 2/4] MN10300: Enable IRQs more in system call exit work path

Enable IRQs when calling schedule() for TIF_NEED_RESCHED and
do_notify_resume().  If interrupts are enabled during do_notify_resume(), a
warning can be seen (see lower down).

Whilst we're at it, resume_userspace can be made local to entry.S as it is not
called outside of there and it can be merged with the part of work_resched that
occurs after schedule() is called.


------------[ cut here ]------------
WARNING: at kernel/softirq.c:160 local_bh_enable+0x42/0xa0()
Modules linked in:
Stack:
  00000000 93d63d88 90009916 901f618c 901f65a8 000000a0 900109b2 93d63db0
  93d62000 93d24d40 00000000 90009940 93d63eb3 93d63dbc 900109b2 00000009
  00000000 93d63dc0 900109b2 93d62000 93d63de0 93d63de0 9016cd1a 901124c8

Call Trace:
 [<90002b8f>] ? show_trace+0x13/0xb4
 [<90002cd0>] show_stack+0x7c/0x84
 [<901124c8>] ? skb_free_head+0x4c/0x54
 [<90002fc9>] dump_stack+0x11/0x18
 [<90009916>] warn_slowpath_common+0x4a/0x5c
 [<900109b2>] ? local_bh_enable+0x42/0xa0
 [<90009940>] warn_slowpath_null+0x18/0x20
 [<900109b2>] ? local_bh_enable+0x42/0xa0
 [<900109b2>] local_bh_enable+0x42/0xa0
 [<9016cd1a>] unix_release_sock+0x86/0x23c
 [<901124c8>] ? skb_free_head+0x4c/0x54
 [<9010e8b5>] ? sk_free+0x31/0x38
 [<9016cef0>] unix_release+0x20/0x28
 [<9010c647>] sock_release+0x17/0x88
 [<9010c874>] sock_close+0x20/0x28
 [<900678e9>] __fput+0xc9/0x1fc
 [<90067a27>] ____fput+0xb/0x10
 [<9001f5a8>] task_work_run+0x64/0x78
 [<9010bda7>] ? sys_connect+0x5b/0x80
 [<90002399>] do_notify_resume+0x53d/0x544
 [<90067dc6>] ? fput+0xce/0xd4
 [<90065117>] ? filp_close+0x5f/0x68
 [<9007bba0>] ? __close_fd+0x7c/0xb0
 [<900026c6>] work_notifysig+0xa/0xc

Signed-off-by: David Howells <dhowells@...hat.com>
Acked-by: Ken Cox <jkc@...hat.com>
---

 arch/mn10300/kernel/entry.S |   18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)


diff --git a/arch/mn10300/kernel/entry.S b/arch/mn10300/kernel/entry.S
index 92c3eea..8754f44 100644
--- a/arch/mn10300/kernel/entry.S
+++ b/arch/mn10300/kernel/entry.S
@@ -113,10 +113,10 @@ syscall_exit_work:
 	and	EPSW_nSL,d0
 	beq	resume_kernel		# returning to supervisor mode
 
-	btst	_TIF_SYSCALL_TRACE,d2
-	beq	work_pending
 	LOCAL_IRQ_ENABLE		# could let syscall_trace_exit() call
 					# schedule() instead
+	btst	_TIF_SYSCALL_TRACE,d2
+	beq	work_pending
 	mov	fp,d0
 	call	syscall_trace_exit[],0	# do_syscall_trace(regs)
 	jmp	resume_userspace
@@ -129,6 +129,7 @@ work_pending:
 work_resched:
 	call	schedule[],0
 
+resume_userspace:
 	# make sure we don't miss an interrupt setting need_resched or
 	# sigpending between sampling and the rti
 	LOCAL_IRQ_DISABLE
@@ -137,6 +138,8 @@ work_resched:
 	mov	(TI_flags,a2),d2
 	btst	_TIF_WORK_MASK,d2
 	beq	restore_all
+
+	LOCAL_IRQ_ENABLE
 	btst	_TIF_NEED_RESCHED,d2
 	bne	work_resched
 
@@ -175,17 +178,6 @@ ret_from_intr:
 	and	EPSW_nSL,d0
 	beq	resume_kernel		# returning to supervisor mode
 
-ENTRY(resume_userspace)
-	# make sure we don't miss an interrupt setting need_resched or
-	# sigpending between sampling and the rti
-	LOCAL_IRQ_DISABLE
-
-	# is there any work to be done on int/exception return?
-	mov	(TI_flags,a2),d2
-	btst	_TIF_WORK_MASK,d2
-	bne	work_pending
-	jmp	restore_all
-
 #ifdef CONFIG_PREEMPT
 ENTRY(resume_kernel)
 	LOCAL_IRQ_DISABLE

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