Revision fea6d607e154cf96ab22254ccb48addfd43d4cb5 authored by Alan Stern on 17 February 2012, 21:25:08 UTC, committed by James Bottomley on 18 February 2012, 14:54:19 UTC
This patch (as1520) fixes a bug in the SCSI layer's power management implementation. LUN scanning can be carried out asynchronously in do_scan_async(), and sd uses an asynchronous thread for the time-consuming parts of disk probing in sd_probe_async(). Currently nothing coordinates these async threads with system sleep transitions; they can and do attempt to continue scanning/probing SCSI devices even after the host adapter has been suspended. As one might expect, the outcome is not ideal. This is what the "prepare" stage of system suspend was created for. After the prepare callback has been called for a host, target, or device, drivers are not allowed to register any children underneath them. Currently the SCSI prepare callback is not implemented; this patch rectifies that omission. For SCSI hosts, the prepare routine calls scsi_complete_async_scans() to wait until async scanning is finished. It might be slightly more efficient to wait only until the host in question has been scanned, but there's currently no way to do that. Besides, during a sleep transition we will ultimately have to wait until all the host scanning has finished anyway. For SCSI devices, the prepare routine calls async_synchronize_full() to wait until sd probing is finished. The routine does nothing for SCSI targets, because asynchronous target scanning is done only as part of host scanning. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: <stable@kernel.org> Signed-off-by: James Bottomley <JBottomley@Parallels.com>
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syscall.c
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <asm/syscall.h>
static int collect_syscall(struct task_struct *target, long *callno,
unsigned long args[6], unsigned int maxargs,
unsigned long *sp, unsigned long *pc)
{
struct pt_regs *regs = task_pt_regs(target);
if (unlikely(!regs))
return -EAGAIN;
*sp = user_stack_pointer(regs);
*pc = instruction_pointer(regs);
*callno = syscall_get_nr(target, regs);
if (*callno != -1L && maxargs > 0)
syscall_get_arguments(target, regs, 0, maxargs, args);
return 0;
}
/**
* task_current_syscall - Discover what a blocked task is doing.
* @target: thread to examine
* @callno: filled with system call number or -1
* @args: filled with @maxargs system call arguments
* @maxargs: number of elements in @args to fill
* @sp: filled with user stack pointer
* @pc: filled with user PC
*
* If @target is blocked in a system call, returns zero with *@callno
* set to the the call's number and @args filled in with its arguments.
* Registers not used for system call arguments may not be available and
* it is not kosher to use &struct user_regset calls while the system
* call is still in progress. Note we may get this result if @target
* has finished its system call but not yet returned to user mode, such
* as when it's stopped for signal handling or syscall exit tracing.
*
* If @target is blocked in the kernel during a fault or exception,
* returns zero with *@callno set to -1 and does not fill in @args.
* If so, it's now safe to examine @target using &struct user_regset
* get() calls as long as we're sure @target won't return to user mode.
*
* Returns -%EAGAIN if @target does not remain blocked.
*
* Returns -%EINVAL if @maxargs is too large (maximum is six).
*/
int task_current_syscall(struct task_struct *target, long *callno,
unsigned long args[6], unsigned int maxargs,
unsigned long *sp, unsigned long *pc)
{
long state;
unsigned long ncsw;
if (unlikely(maxargs > 6))
return -EINVAL;
if (target == current)
return collect_syscall(target, callno, args, maxargs, sp, pc);
state = target->state;
if (unlikely(!state))
return -EAGAIN;
ncsw = wait_task_inactive(target, state);
if (unlikely(!ncsw) ||
unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) ||
unlikely(wait_task_inactive(target, state) != ncsw))
return -EAGAIN;
return 0;
}
EXPORT_SYMBOL_GPL(task_current_syscall);
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