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Commit 92649494 authored by Mike Frysinger's avatar Mike Frysinger
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Blackfin: optimize fixed code handling for the most common case 



The majority of the time we are returning to user space, it is not in the
fixed atomic code region.  So rather than branch to a function where we
check the PC and return, do the check inline and branch only when needed.

Also, tweak some of the fixed code handling based on assumptions we are
aware of but cannot be expressed in C.

Signed-off-by: default avatarMike Frysinger <vapier@gentoo.org>
parent dac98174

arch/blackfin/kernel/process.c

+2 −8
Original line number Diff line number Diff line
@@ -282,24 +282,18 @@ void finish_atomic_sections (struct pt_regs *regs) 
{

	int __user *up0 = (int __user *)regs->p0;



	if (regs->pc < ATOMIC_SEQS_START || regs->pc >= ATOMIC_SEQS_END)

		return;



	switch (regs->pc) {

	case ATOMIC_XCHG32 + 2:

		put_user(regs->r1, up0);

		regs->pc += 2;

		regs->pc = ATOMIC_XCHG32 + 4;

		break;



	case ATOMIC_CAS32 + 2:

	case ATOMIC_CAS32 + 4:

		if (regs->r0 == regs->r1)

			put_user(regs->r2, up0);

		regs->pc = ATOMIC_CAS32 + 8;

		break;

	case ATOMIC_CAS32 + 6:

			put_user(regs->r2, up0);

		regs->pc += 2;

		regs->pc = ATOMIC_CAS32 + 8;

		break;



	case ATOMIC_ADD32 + 2:

arch/blackfin/mach-common/entry.S

+6 −0
Original line number Diff line number Diff line
@@ -1025,6 +1025,12 @@ ENTRY(_schedule_and_signal_from_int) 
#endif

	sti r0;



	/* finish the userspace "atomic" functions for it */

	r1 = FIXED_CODE_END;

	r2 = [sp + PT_PC];

	cc = r1 <= r2;

	if cc jump .Lresume_userspace (bp);



	r0 = sp;

	sp += -12;

	call _finish_atomic_sections;