Commit a646ef39 authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Heiko Carstens
Browse files

s390/jump_label: replace stop_machine with smp_call_function 



The use of stop_machine to replace the mask bits of the jump label branch
is a very heavy-weight operation. This is in fact not necessary, the
mask of the branch can simply be updated, followed by a signal processor
to all the other CPUs to force them to pick up the modified instruction.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
[heiko.carstens@de.ibm.com]: Change jump_label_make_nop() so we get
                             brcl 0,offset instead of brcl 0,0. This
                             makes sure that only the mask part of the
                             instruction gets changed when updated.
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
parent f2c7c76c

arch/s390/kernel/jump_label.c

+5 −13
Original line number Diff line number Diff line
@@ -22,9 +22,9 @@ struct insn_args { 


static void jump_label_make_nop(struct jump_entry *entry, struct insn *insn)

{

	/* brcl 0,0 */

	/* brcl 0,offset */

	insn->opcode = 0xc004;

	insn->offset = 0;

	insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1;

}



static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
@@ -77,23 +77,15 @@ static void __jump_label_transform(struct jump_entry *entry, 
	s390_kernel_write(code, &new, sizeof(new));

}



static int __sm_arch_jump_label_transform(void *data)

static void __jump_label_sync(void *dummy)

{

	struct insn_args *args = data;



	__jump_label_transform(args->entry, args->type, 0);

	return 0;

}



void arch_jump_label_transform(struct jump_entry *entry,

			       enum jump_label_type type)

{

	struct insn_args args;



	args.entry = entry;

	args.type = type;



	stop_machine_cpuslocked(__sm_arch_jump_label_transform, &args, NULL);

	__jump_label_transform(entry, type, 0);

	smp_call_function(__jump_label_sync, NULL, 1);

}



void arch_jump_label_transform_static(struct jump_entry *entry,

arch/s390/mm/maccess.c

+5 −4
Original line number Diff line number Diff line
@@ -52,21 +52,22 @@ static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t siz 
 * Therefore we have a read-modify-write sequence: the function reads eight

 * bytes from destination at an eight byte boundary, modifies the bytes

 * requested and writes the result back in a loop.

 *

 * Note: this means that this function may not be called concurrently on

 *	 several cpus with overlapping words, since this may potentially

 *	 cause data corruption.

 */

static DEFINE_SPINLOCK(s390_kernel_write_lock);



void notrace s390_kernel_write(void *dst, const void *src, size_t size)

{

	unsigned long flags;

	long copied;



	spin_lock_irqsave(&s390_kernel_write_lock, flags);

	while (size) {

		copied = s390_kernel_write_odd(dst, src, size);

		dst += copied;

		src += copied;

		size -= copied;

	}

	spin_unlock_irqrestore(&s390_kernel_write_lock, flags);

}



static int __memcpy_real(void *dest, void *src, size_t count)