3.16.55-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: "Maciej W. Rozycki" <macro@xxxxxxxxxxxxxx> commit 03dce595270f22d59a6f37e9170287c1afd94bc2 upstream. Fix "BUG: using smp_processor_id() in preemptible" reported in accesses to thread's FPU defaults: the value to initialise FSCR to at program startup, the FCSR r/w mask and the contents of FIR in full FPU emulation, removing a regression introduced with 9b26616c [MIPS: Respect the ISA level in FCSR handling] and f6843626 [MIPS: math-emu: Set FIR feature flags for full emulation]. Use `boot_cpu_data' to obtain the data from, following the approach that `cpu_has_*' macros take and avoiding the call to `smp_processor_id' made in the reference to `current_cpu_data'. The contents of FSCR have to be consistent across processors in an SMP system, the settings there must not change as a thread is migrated across processors. And the contents of FIR are guaranteed to be consistent in FPU emulation, by definition. Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxxxxx> Tested-by: Ezequiel Garcia <ezequiel.garcia@xxxxxxxxxx> Tested-by: Paul Martin <paul.martin@xxxxxxxxxxxxxxx> Cc: Markos Chandras <Markos.Chandras@xxxxxxxxxx> Cc: James Hogan <james.hogan@xxxxxxxxxx> Cc: linux-mips@xxxxxxxxxxxxxx Patchwork: https://patchwork.linux-mips.org/patch/10030/ Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx> [bwh: Backported to 3.16: - Drop change in cop1_cfc() - Adjust context] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- --- a/arch/mips/include/asm/elf.h +++ b/arch/mips/include/asm/elf.h @@ -277,7 +277,7 @@ do { \ \ current->thread.abi = &mips_abi; \ \ - current->thread.fpu.fcr31 = current_cpu_data.fpu_csr31; \ + current->thread.fpu.fcr31 = boot_cpu_data.fpu_csr31; \ } while (0) #endif /* CONFIG_32BIT */ @@ -337,7 +337,7 @@ do { \ else \ current->thread.abi = &mips_abi; \ \ - current->thread.fpu.fcr31 = current_cpu_data.fpu_csr31; \ + current->thread.fpu.fcr31 = boot_cpu_data.fpu_csr31; \ \ p = personality(current->personality); \ if (p != PER_LINUX32 && p != PER_LINUX) \ --- a/arch/mips/kernel/ptrace.c +++ b/arch/mips/kernel/ptrace.c @@ -177,7 +177,7 @@ int ptrace_setfpregs(struct task_struct __get_user(value, data + 64); fcr31 = child->thread.fpu.fcr31; - mask = current_cpu_data.fpu_msk31; + mask = boot_cpu_data.fpu_msk31; child->thread.fpu.fcr31 = (value & ~mask) | (fcr31 & mask); /* FIR may not be written. */ --- a/arch/mips/math-emu/cp1emu.c +++ b/arch/mips/math-emu/cp1emu.c @@ -934,7 +934,7 @@ emul: * Preserve read-only bits, * and convert to ieee library modes */ - mask = current_cpu_data.fpu_msk31; + mask = boot_cpu_data.fpu_msk31; ctx->fcr31 = (value & ~(mask | FPU_CSR_RM)) | (ctx->fcr31 & mask) | modeindex(value);