arm64: smp: Prevent raw_smp_processor_id() recursion
authorRobin Murphy <robin.murphy@arm.com>
Thu, 1 Dec 2016 15:55:13 +0000 (15:55 +0000)
committerCatalin Marinas <catalin.marinas@arm.com>
Fri, 2 Dec 2016 10:50:57 +0000 (10:50 +0000)
commit34a6980c82fb1342e7064844c95aa4cf933e5ecc
treead9e7c8f741ee27d78a15c53d36926a447d7031d
parent00cc2e07453796dc99a32c390ded964f33ac7e89
arm64: smp: Prevent raw_smp_processor_id() recursion

Under CONFIG_DEBUG_PREEMPT=y, this_cpu_ptr() ends up calling back into
raw_smp_processor_id(), resulting in some hilariously catastrophic
infinite recursion. In the normal case, we have:

  #define this_cpu_ptr(ptr) raw_cpu_ptr(ptr)

and everything is dandy. However for CONFIG_DEBUG_PREEMPT, this_cpu_ptr()
is defined in terms of my_cpu_offset, wherein the fun begins:

  #define my_cpu_offset per_cpu_offset(smp_processor_id())
  ...
  #define smp_processor_id() debug_smp_processor_id()
  ...
  notrace unsigned int debug_smp_processor_id(void)
  {
   return check_preemption_disabled("smp_processor_id", "");
  ...
  notrace static unsigned int check_preemption_disabled(const char *what1,
   const char *what2)
  {
   int this_cpu = raw_smp_processor_id();

and bang. Use raw_cpu_ptr() directly to avoid that.

Fixes: 57c82954e77f ("arm64: make cpu number a percpu variable")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
arch/arm64/include/asm/smp.h