From 7daef8f261e509bea79ea3b0076e624135259bc1 Mon Sep 17 00:00:00 2001 From: Paul Burton Date: Fri, 11 Jul 2014 16:47:05 +0100 Subject: [PATCH] MIPS: consistently clear MSA flags when starting & copying threads The TIF_MSA_CTX_LIVE flag (indicating that a task has MSA context which needs to be preserved) was being cleared in start_thread, but the TIF_USEDMSA flag (indicating that a task has used MSA in this timeslice) was not. In copy_thread neither flag was cleared, but both need to be. Without clearing these flags the kernel will proceed to attempt to save MSA context when the task is context switched out, and if the task had not used MSA in the meantime then it will fail because MSA or the FPU are disabled. The end result is typically: do_cpu invoked from kernel context![#1]: CPU: 0 PID: 99 Comm: sh Not tainted 3.16.0-rc4-00025-g6dc9476-dirty #88 task: 8f23dc60 ti: 8f1d8000 task.ti: 8f1d8000 ... Call Trace: [<8010edbc>] resume+0x5c/0x280 [<80481e0c>] __schedule+0x370/0x800 [<80104838>] work_resched+0x8/0x2c Fix by consistently clearing both flags in both functions. Signed-off-by: Paul Burton Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/7309/ Signed-off-by: Ralf Baechle --- arch/mips/kernel/process.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c index 2dafceb0d0c601..636b0745d7c7e5 100644 --- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -66,6 +66,7 @@ void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp) clear_used_math(); clear_fpu_owner(); init_dsp(); + clear_thread_flag(TIF_USEDMSA); clear_thread_flag(TIF_MSA_CTX_LIVE); disable_msa(); regs->cp0_epc = pc; @@ -141,6 +142,8 @@ int copy_thread(unsigned long clone_flags, unsigned long usp, childregs->cp0_status &= ~(ST0_CU2|ST0_CU1); clear_tsk_thread_flag(p, TIF_USEDFPU); + clear_tsk_thread_flag(p, TIF_USEDMSA); + clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE); #ifdef CONFIG_MIPS_MT_FPAFF clear_tsk_thread_flag(p, TIF_FPUBOUND);