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Commit 18698917 authored by Andreas Mohr's avatar Andreas Mohr Committed by Linus Torvalds
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[PATCH] cpu_relax(): smpboot.c 



Add cpu_relax() to various smpboot.c init loops.  cpu_relax() always implies a
barrier (according to Arjan), so remove those as well.

Signed-off-by: default avatarAndreas Mohr <andi@lisas.de>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e75eac33

arch/i386/kernel/smpboot.c

+8 −6
Original line number Diff line number Diff line
@@ -257,7 +257,7 @@ static void __init synchronize_tsc_bp (void) 
		 * all APs synchronize but they loop on '== num_cpus'

		 */

		while (atomic_read(&tsc_count_start) != num_booting_cpus()-1)

			mb();

			cpu_relax();

		atomic_set(&tsc_count_stop, 0);

		wmb();

		/*
@@ -276,7 +276,7 @@ static void __init synchronize_tsc_bp (void) 
		 * Wait for all APs to leave the synchronization point:

		 */

		while (atomic_read(&tsc_count_stop) != num_booting_cpus()-1)

			mb();

			cpu_relax();

		atomic_set(&tsc_count_start, 0);

		wmb();

		atomic_inc(&tsc_count_stop);
@@ -333,19 +333,21 @@ static void __init synchronize_tsc_ap (void) 
	 * this gets called, so we first wait for the BP to

	 * finish SMP initialization:

	 */

	while (!atomic_read(&tsc_start_flag)) mb();

	while (!atomic_read(&tsc_start_flag))

		cpu_relax();



	for (i = 0; i < NR_LOOPS; i++) {

		atomic_inc(&tsc_count_start);

		while (atomic_read(&tsc_count_start) != num_booting_cpus())

			mb();

			cpu_relax();



		rdtscll(tsc_values[smp_processor_id()]);

		if (i == NR_LOOPS-1)

			write_tsc(0, 0);



		atomic_inc(&tsc_count_stop);

		while (atomic_read(&tsc_count_stop) != num_booting_cpus()) mb();

		while (atomic_read(&tsc_count_stop) != num_booting_cpus())

			cpu_relax();

	}

}

#undef NR_LOOPS
@@ -1433,7 +1435,7 @@ int __devinit __cpu_up(unsigned int cpu) 
	/* Unleash the CPU! */

	cpu_set(cpu, smp_commenced_mask);

	while (!cpu_isset(cpu, cpu_online_map))

		mb();

		cpu_relax();

	return 0;

}