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Revision ea0854170c95245a258b386c7a9314399c949fe0 authored by Shaohui Zheng on 02 February 2010, 21:44:16 UTC, committed by Linus Torvalds on 03 February 2010, 02:11:23 UTC 
memory hotplug: fix a bug on /dev/mem for 64-bit kernels
 
Newly added memory can not be accessed via /dev/mem, because we do not
update the variables high_memory, max_pfn and max_low_pfn.

Add a function update_end_of_memory_vars() to update these variables for
64-bit kernels.

[akpm@linux-foundation.org: simplify comment]
Signed-off-by: Shaohui Zheng <shaohui.zheng@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Li Haicheng <haicheng.li@intel.com>
Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent a225a5c
Raw File
disable-tsc-on-off-stress-test.c 
/*
 * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
 *
 * Tests if the control register is updated correctly
 * when set with prctl()
 *
 * Warning: this test will cause a very high load for a few seconds
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <inttypes.h>
#include <wait.h>


#include <sys/prctl.h>
#include <linux/prctl.h>

/* Get/set the process' ability to use the timestamp counter instruction */
#ifndef PR_GET_TSC
#define PR_GET_TSC 25
#define PR_SET_TSC 26
# define PR_TSC_ENABLE		1   /* allow the use of the timestamp counter */
# define PR_TSC_SIGSEGV		2   /* throw a SIGSEGV instead of reading the TSC */
#endif

/* snippet from wikipedia :-) */

uint64_t rdtsc() {
uint32_t lo, hi;
/* We cannot use "=A", since this would use %rax on x86_64 */
__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
return (uint64_t)hi << 32 | lo;
}

int should_segv = 0;

void sigsegv_cb(int sig)
{
	if (!should_segv)
	{
		fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
		exit(0);
	}
	if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
	{
		perror("prctl");
		exit(0);
	}
	should_segv = 0;

	rdtsc();
}

void task(void)
{
	signal(SIGSEGV, sigsegv_cb);
	alarm(10);
	for(;;)
	{
		rdtsc();
		if (should_segv)
		{
			fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
			exit(0);
		}
		if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
		{
			perror("prctl");
			exit(0);
		}
		should_segv = 1;
	}
}


int main(int argc, char **argv)
{
	int n_tasks = 100, i;

	fprintf(stderr, "[No further output means we're allright]\n");

	for (i=0; i<n_tasks; i++)
		if (fork() == 0)
			task();

	for (i=0; i<n_tasks; i++)
		wait(NULL);

	exit(0);
}
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