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Revision bb94a406682770a35305daaa241ccdb7cab399de authored by Alan Stern on 21 February 2012, 18:16:32 UTC, committed by Greg Kroah-Hartman on 22 February 2012, 00:29:15 UTC 
usb-storage: fix freezing of the scanning thread
 
This patch (as1521b) fixes the interaction between usb-storage's
scanning thread and the freezer.  The current implementation has a
race: If the device is unplugged shortly after being plugged in and
just as a system sleep begins, the scanning thread may get frozen
before the khubd task.  Khubd won't be able to freeze until the
disconnect processing is complete, and the disconnect processing can't
proceed until the scanning thread finishes, so the sleep transition
will fail.

The implementation in the 3.2 kernel suffers from an additional
problem.  There the scanning thread calls set_freezable_with_signal(),
and the signals sent by the freezer will mess up the thread's I/O
delays, which are all interruptible.

The solution to both problems is the same: Replace the kernel thread
used for scanning with a delayed-work routine on the system freezable
work queue.  Freezable work queues have the nice property that you can
cancel a work item even while the work queue is frozen, and no signals
are needed.

The 3.2 version of this patch solves the problem in Bugzilla #42730.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
CC: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 parent 9a9a71b
Raw File
ioremap.c 
/*
 * Re-map IO memory to kernel address space so that we can access it.
 * This is needed for high PCI addresses that aren't mapped in the
 * 640k-1MB IO memory area on PC's
 *
 * (C) Copyright 1995 1996 Linus Torvalds
 */
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/io.h>
#include <linux/module.h>
#include <asm/cacheflush.h>
#include <asm/pgtable.h>

static int ioremap_pte_range(pmd_t *pmd, unsigned long addr,
		unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
{
	pte_t *pte;
	u64 pfn;

	pfn = phys_addr >> PAGE_SHIFT;
	pte = pte_alloc_kernel(pmd, addr);
	if (!pte)
		return -ENOMEM;
	do {
		BUG_ON(!pte_none(*pte));
		set_pte_at(&init_mm, addr, pte, pfn_pte(pfn, prot));
		pfn++;
	} while (pte++, addr += PAGE_SIZE, addr != end);
	return 0;
}

static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr,
		unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
{
	pmd_t *pmd;
	unsigned long next;

	phys_addr -= addr;
	pmd = pmd_alloc(&init_mm, pud, addr);
	if (!pmd)
		return -ENOMEM;
	do {
		next = pmd_addr_end(addr, end);
		if (ioremap_pte_range(pmd, addr, next, phys_addr + addr, prot))
			return -ENOMEM;
	} while (pmd++, addr = next, addr != end);
	return 0;
}

static inline int ioremap_pud_range(pgd_t *pgd, unsigned long addr,
		unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
{
	pud_t *pud;
	unsigned long next;

	phys_addr -= addr;
	pud = pud_alloc(&init_mm, pgd, addr);
	if (!pud)
		return -ENOMEM;
	do {
		next = pud_addr_end(addr, end);
		if (ioremap_pmd_range(pud, addr, next, phys_addr + addr, prot))
			return -ENOMEM;
	} while (pud++, addr = next, addr != end);
	return 0;
}

int ioremap_page_range(unsigned long addr,
		       unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
{
	pgd_t *pgd;
	unsigned long start;
	unsigned long next;
	int err;

	BUG_ON(addr >= end);

	start = addr;
	phys_addr -= addr;
	pgd = pgd_offset_k(addr);
	do {
		next = pgd_addr_end(addr, end);
		err = ioremap_pud_range(pgd, addr, next, phys_addr+addr, prot);
		if (err)
			break;
	} while (pgd++, addr = next, addr != end);

	flush_cache_vmap(start, end);

	return err;
}
EXPORT_SYMBOL_GPL(ioremap_page_range);
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