Hi Paul, Unfortunately, I remember that sdbbp instruction can be executed in user mode. so, $gp may not always point to thread info. On Mon, Jun 11, 2018 at 9:38 AM, <r@xxxxxx> wrote: > From: Heiher <r@xxxxxx> > > 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. > > Signed-off-by: Heiher <r@xxxxxx> > --- > arch/mips/kernel/genex.S | 44 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 44 insertions(+) > > diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S > index 37b9383eacd3..fec6256bac1e 100644 > --- a/arch/mips/kernel/genex.S > +++ b/arch/mips/kernel/genex.S > @@ -354,16 +354,54 @@ 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) > + > + lw k1, TI_CPU(gp) > + 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 > + lw k1, TI_CPU(gp) > + 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 +415,12 @@ 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 > -- > 2.17.1 > -- Best regards! Hev https://hev.cc
