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Commit 19dad35f authored by Russell King's avatar Russell King
Browse files

ARM: vfp: ensure that thread flushing works if preempted 



Prevent a preemption event causing the initialized VFP state being
overwritten by ensuring that the VFP hardware access is disabled
prior to starting initialization.  We can then do this in safety
while still allowing preemption to occur.

Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent f8f2a852

arch/arm/vfp/vfpmodule.c

+13 −10
Original line number Diff line number Diff line
@@ -89,24 +89,27 @@ static void vfp_thread_flush(struct thread_info *thread) 
	union vfp_state *vfp = &thread->vfpstate;

	unsigned int cpu;



	memset(vfp, 0, sizeof(union vfp_state));



	vfp->hard.fpexc = FPEXC_EN;

	vfp->hard.fpscr = FPSCR_ROUND_NEAREST;

#ifdef CONFIG_SMP

	vfp->hard.cpu = NR_CPUS;

#endif



	/*

	 * Disable VFP to ensure we initialize it first.  We must ensure

	 * that the modification of vfp_current_hw_state[] and hardware disable

	 * are done for the same CPU and without preemption.

	 * that the modification of vfp_current_hw_state[] and hardware

	 * disable are done for the same CPU and without preemption.

	 *

	 * Do this first to ensure that preemption won't overwrite our

	 * state saving should access to the VFP be enabled at this point.

	 */

	cpu = get_cpu();

	if (vfp_current_hw_state[cpu] == vfp)

		vfp_current_hw_state[cpu] = NULL;

	fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);

	put_cpu();



	memset(vfp, 0, sizeof(union vfp_state));



	vfp->hard.fpexc = FPEXC_EN;

	vfp->hard.fpscr = FPSCR_ROUND_NEAREST;

#ifdef CONFIG_SMP

	vfp->hard.cpu = NR_CPUS;

#endif

}



static void vfp_thread_exit(struct thread_info *thread)