Commit 90089759 authored May 24, 2020 by Guo Ren

csky: Fixup CONFIG_PREEMPT panic



log:
[    0.13373200] Calibrating delay loop...
[    0.14077600] ------------[ cut here ]------------
[    0.14116700] WARNING: CPU: 0 PID: 0 at kernel/sched/core.c:3790 preempt_count_add+0xc8/0x11c
[    0.14348000] DEBUG_LOCKS_WARN_ON((preempt_count() < 0))Modules linked in:
[    0.14395100] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.0 #7
[    0.14410800]
[    0.14427400] Call Trace:
[    0.14450700] [<807cd226>] dump_stack+0x8a/0xe4
[    0.14473500] [<80072792>] __warn+0x10e/0x15c
[    0.14495900] [<80072852>] warn_slowpath_fmt+0x72/0xc0
[    0.14518600] [<800a5240>] preempt_count_add+0xc8/0x11c
[    0.14544900] [<807ef918>] _raw_spin_lock+0x28/0x68
[    0.14572600] [<800e0eb8>] vprintk_emit+0x84/0x2d8
[    0.14599000] [<800e113a>] vprintk_default+0x2e/0x44
[    0.14625100] [<800e2042>] vprintk_func+0x12a/0x1d0
[    0.14651300] [<800e1804>] printk+0x30/0x48
[    0.14677600] [<80008052>] lockdep_init+0x12/0xb0
[    0.14703800] [<80002080>] start_kernel+0x558/0x7f8
[    0.14730000] [<800052bc>] csky_start+0x58/0x94
[    0.14756600] irq event stamp: 34
[    0.14775100] hardirqs last  enabled at (33): [<80067370>] ret_from_exception+0x2c/0x72
[    0.14793700] hardirqs last disabled at (34): [<800e0eae>] vprintk_emit+0x7a/0x2d8
[    0.14812300] softirqs last  enabled at (32): [<800655b0>] __do_softirq+0x578/0x6d8
[    0.14830800] softirqs last disabled at (25): [<8007b3b8>] irq_exit+0xec/0x128

The preempt_count of reg could be destroyed after csky_do_IRQ without reload
from memory.

After reference to other architectures (arm64, riscv), we move preempt entry
into ret_from_exception and disable irq at the beginning of
ret_from_exception instead of RESTORE_ALL.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Reported-by: Lu Baoquan <lu.baoquan@intellif.com>

parent 9cb1fd0e

arch/csky/abiv1/inc/abi/entry.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -80,7 +80,6 @@
		.endm

		.macro RESTORE_ALL
		psrclr ie
		ldw lr, (sp, 4)
		ldw a0, (sp, 8)
		mtcr a0, epc

arch/csky/abiv2/inc/abi/entry.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -63,7 +63,6 @@
		.endm

		.macro RESTORE_ALL
		psrclr ie
		ldw tls, (sp, 0)
		ldw lr, (sp, 4)
		ldw a0, (sp, 8)

arch/csky/kernel/entry.S

+11 −25

Original line number	Diff line number	Diff line
		@@ -208,9 +208,9 @@ ENTRY(ret_from_fork)
		jbsr syscall_trace_exit

		ret_from_exception:
		psrclr ie
		ld syscallid, (sp, LSAVE_PSR)
		btsti syscallid, 31
		bt 1f

		/*
		* Load address of current->thread_info, Then get address of task_struct
		@@ -220,11 +220,20 @@ ret_from_exception:
		bmaski r10, THREAD_SHIFT
		andn r9, r10

		bt 1f
		ldw r12, (r9, TINFO_FLAGS)
		andi r12, (_TIF_SIGPENDING \| _TIF_NOTIFY_RESUME \| _TIF_NEED_RESCHED \| _TIF_UPROBE)
		cmpnei r12, 0
		bt exit_work
		1:
		#ifdef CONFIG_PREEMPTION
		ldw r12, (r9, TINFO_PREEMPT)
		cmpnei r12, 0
		bt 2f
		jbsr preempt_schedule_irq /* irq en/disable is done inside */
		2:
		#endif

		#ifdef CONFIG_TRACE_IRQFLAGS
		ld r10, (sp, LSAVE_PSR)
		btsti r10, 6
		@@ -241,6 +250,7 @@ exit_work:
		btsti r12, TIF_NEED_RESCHED
		bt work_resched

		psrset ie
		mov a0, sp
		mov a1, r12
		jmpi do_notify_resume
		@@ -291,34 +301,10 @@ ENTRY(csky_irq)
		jbsr trace_hardirqs_off
		#endif

		#ifdef CONFIG_PREEMPTION
		mov r9, sp /* Get current stack pointer */
		bmaski r10, THREAD_SHIFT
		andn r9, r10 /* Get thread_info */

		/*
		* Get task_struct->stack.preempt_count for current,
		* and increase 1.
		*/
		ldw r12, (r9, TINFO_PREEMPT)
		addi r12, 1
		stw r12, (r9, TINFO_PREEMPT)
		#endif

		mov a0, sp
		jbsr csky_do_IRQ

		#ifdef CONFIG_PREEMPTION
		subi r12, 1
		stw r12, (r9, TINFO_PREEMPT)
		cmpnei r12, 0
		bt 2f
		ldw r12, (r9, TINFO_FLAGS)
		btsti r12, TIF_NEED_RESCHED
		bf 2f
		jbsr preempt_schedule_irq /* irq en/disable is done inside */
		#endif
		2:
		jmpi ret_from_exception

		/*