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Unverified Commit c8bf3805 authored by Heiher's avatar Heiher Committed by Paul Burton
Browse files

MIPS: Fix ejtag handler on SMP 



On SMP systems, the shared ejtag debug buffer may be overwritten by
other cores, because every cores can generate ejtag exception at
same time.

Unfortunately, in that context, it's difficult to relax more registers
to access per cpu buffers. so use ll/sc to serialize the access.

[paul.burton@mips.com:
  This could in theory be backported at least as far back as the
  beginning of the git era, however in general it's exceedingly rare
  that anyone would hit this without further changes, so it doesn't seem
  worthwhile marking for backport.]

Signed-off-by: default avatarHeiher <r@hev.cc>
Patchwork: https://patchwork.linux-mips.org/patch/19507/


Signed-off-by: default avatarPaul Burton <paul.burton@mips.com>
Cc: jhogan@kernel.org
Cc: ralf@linux-mips.org
parent be462bd9

arch/mips/kernel/genex.S

+46 −0
Original line number Diff line number Diff line
@@ -354,16 +354,56 @@ NESTED(ejtag_debug_handler, PT_SIZE, sp) 
	sll	k0, k0, 30	# Check for SDBBP.

	bgez	k0, ejtag_return



#ifdef CONFIG_SMP

1:	PTR_LA	k0, ejtag_debug_buffer_spinlock

	ll	k0, 0(k0)

	bnez	k0, 1b

	PTR_LA	k0, ejtag_debug_buffer_spinlock

	sc	k0, 0(k0)

	beqz	k0, 1b

# ifdef CONFIG_WEAK_REORDERING_BEYOND_LLSC

	sync

# endif



	PTR_LA	k0, ejtag_debug_buffer

	LONG_S	k1, 0(k0)



	ASM_CPUID_MFC0 k1, ASM_SMP_CPUID_REG

	PTR_SRL	k1, SMP_CPUID_PTRSHIFT

	PTR_SLL	k1, LONGLOG

	PTR_LA	k0, ejtag_debug_buffer_per_cpu

	PTR_ADDU k0, k1



	PTR_LA	k1, ejtag_debug_buffer

	LONG_L	k1, 0(k1)

	LONG_S	k1, 0(k0)



	PTR_LA	k0, ejtag_debug_buffer_spinlock

	sw	zero, 0(k0)

#else

	PTR_LA	k0, ejtag_debug_buffer

	LONG_S	k1, 0(k0)

#endif



	SAVE_ALL

	move	a0, sp

	jal	ejtag_exception_handler

	RESTORE_ALL



#ifdef CONFIG_SMP

	ASM_CPUID_MFC0 k1, ASM_SMP_CPUID_REG

	PTR_SRL	k1, SMP_CPUID_PTRSHIFT

	PTR_SLL	k1, LONGLOG

	PTR_LA	k0, ejtag_debug_buffer_per_cpu

	PTR_ADDU k0, k1

	LONG_L	k1, 0(k0)

#else

	PTR_LA	k0, ejtag_debug_buffer

	LONG_L	k1, 0(k0)

#endif



ejtag_return:

	back_to_back_c0_hazard

	MFC0	k0, CP0_DESAVE

	.set	mips32

	deret
@@ -377,6 +417,12 @@ ejtag_return: 
	.data

EXPORT(ejtag_debug_buffer)

	.fill	LONGSIZE

#ifdef CONFIG_SMP

EXPORT(ejtag_debug_buffer_spinlock)

	.fill	LONGSIZE

EXPORT(ejtag_debug_buffer_per_cpu)

	.fill	LONGSIZE * NR_CPUS

#endif

	.previous



	__INIT