Commit bd239f1e authored Apr 21, 2016 by Paul Burton Committed by Ralf Baechle May 13, 2016

MIPS: Disable preemption during prctl(PR_SET_FP_MODE, ...)



Whilst a PR_SET_FP_MODE prctl is performed there are decisions made
based upon whether the task is executing on the current CPU. This may
change if we're preempted, so disable preemption to avoid such changes
for the lifetime of the mode switch.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Fixes: 9791554b ("MIPS,prctl: add PR_[GS]ET_FP_MODE prctl options for MIPS")
Reviewed-by: Maciej W. Rozycki <macro@imgtec.com>
Tested-by: Aurelien Jarno <aurelien@aurel32.net>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: stable <stable@vger.kernel.org> # v4.0+
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13144/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

parent e70ac023

arch/mips/kernel/process.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -597,6 +597,9 @@ int mips_set_process_fp_mode(struct task_struct *task, unsigned int value)
		if (!(value & PR_FP_MODE_FR) && cpu_has_fpu && cpu_has_mips_r6)
		return -EOPNOTSUPP;

		/* Proceed with the mode switch */
		preempt_disable();

		/* Save FP & vector context, then disable FPU & MSA */
		if (task->signal == current->signal)
		lose_fpu(1);
		@@ -655,6 +658,7 @@ int mips_set_process_fp_mode(struct task_struct *task, unsigned int value)

		/* Allow threads to use FP again */
		atomic_set(&task->mm->context.fp_mode_switching, 0);
		preempt_enable();

		return 0;
		}