333 lines
10 KiB
C
333 lines
10 KiB
C
/****************************************************************************
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* mm/mm_heap/mm_sem.c
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*
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* Copyright (C) 2007-2009, 2013, 2017-2018 Gregory Nutt. All rights
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* reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <unistd.h>
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#include <semaphore.h>
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#include <errno.h>
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#include <assert.h>
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#include <nuttx/semaphore.h>
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#include <nuttx/mm/mm.h>
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#ifdef CONFIG_SMP
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# include <nuttx/irq.h>
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#endif
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* Internal nxsem_* interfaces are not available in the user space in
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* PROTECTED and KERNEL builds. In that context, the application semaphore
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* interfaces must be used. The differences between the two sets of
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* interfaces are: (1) the nxsem_* interfaces do not cause cancellation
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* points and (2) they do not modify the errno variable.
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*
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* See additional definitions in include/nuttx/semaphore.h
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*
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* REVISIT: The fact that sem_wait() is a cancellation point is an issue
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* and does cause a violation: It makes all of the memory management
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* interfaces into cancellation points when used from user space in the
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* PROTECTED and KERNEL builds.
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*/
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#if defined(CONFIG_BUILD_FLAT) || defined(__KERNEL__)
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# define _SEM_GETERROR(r)
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#else
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# define _SEM_GETERROR(r) (r) = -errno
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#endif
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/* This is a special value that indicates that there is no holder of the
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* semaphore. The valid range of PIDs is 0-32767 and any value outside of
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* that range could be used (except -ESRCH which is a special return value
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* from getpid())
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*/
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#define NO_HOLDER ((pid_t)-1)
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/* Define MONITOR_MM_SEMAPHORE to enable semaphore state monitoring */
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#ifdef MONITOR_MM_SEMAPHORE
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# include <debug.h>
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# define msemerr _err
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# define msemwarn _warn
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# define mseminfo _info
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#else
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# ifdef CONFIG_CPP_HAVE_VARARGS
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# define msemerr(x...)
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# define msemwarn(x...)
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# define mseminfo(x...)
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# else
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# define msemerr (void)
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# define msemwarn (void)
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# define mseminfo (void)
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# endif
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: mm_seminitialize
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*
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* Description:
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* Initialize the MM mutex
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*
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****************************************************************************/
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void mm_seminitialize(FAR struct mm_heap_s *heap)
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{
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/* Initialize the MM semaphore to one (to support one-at-a-time access to
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* private data sets).
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*/
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(void)nxsem_init(&heap->mm_semaphore, 0, 1);
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heap->mm_holder = NO_HOLDER;
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heap->mm_counts_held = 0;
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}
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/****************************************************************************
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* Name: mm_trysemaphore
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*
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* Description:
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* Try to take the MM mutex. This is called only from the OS in certain
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* conditions when it is necessary to have exclusive access to the memory
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* manager but it is impossible to wait on a semaphore (e.g., the idle
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* process when it performs its background memory cleanup).
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*
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****************************************************************************/
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int mm_trysemaphore(FAR struct mm_heap_s *heap)
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{
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#ifdef CONFIG_SMP
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irqstate_t flags = enter_critical_section();
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#endif
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pid_t my_pid = getpid();
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int ret;
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/* getpid() returns the task ID of the task at the head of the ready-to-
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* run task list. mm_trysemaphore() may be called during context
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* switches. There are certain situations during context switching when
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* the OS data structures are in flux and where the current task (i.e.,
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* the task at the head of the ready-to-run task list) is not actually
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* running. Granting the semaphore access in that case is known to result
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* in heap corruption as in the following failure scenario.
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*
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* ---------------------------- -------------------------------
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* TASK A TASK B
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* ---------------------------- -------------------------------
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* Begins memory allocation.
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* - Holder is set to TASK B
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* <---- Task B preempted, Task A runs
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* Task A exits
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* - Current task set to Task B
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* Free tcb and stack memory
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* - Since holder is Task B,
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* memory manager is re-
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* entered, and
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* - Heap is corrupted.
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* ---------------------------- -------------------------------
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*
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* This is handled by getpid(): If the case where Task B is not actually
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* running, then getpid() will return the special value -ESRCH. That will
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* avoid taking the fatal 'if' logic and will fall through to use the
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* 'else', albeit with a nonsensical PID value.
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*/
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/* Does the current task already hold the semaphore? Is the current
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* task actually running?
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*/
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if (heap->mm_holder == my_pid)
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{
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/* Yes, just increment the number of references held by the current
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* task.
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*/
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heap->mm_counts_held++;
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ret = OK;
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}
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else
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{
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/* Try to take the semaphore */
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ret = _SEM_TRYWAIT(&heap->mm_semaphore);
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if (ret < 0)
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{
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_SEM_GETERROR(ret);
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goto errout;
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}
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/* We have it. Claim the heap for the current task and return */
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heap->mm_holder = my_pid;
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heap->mm_counts_held = 1;
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ret = OK;
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}
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errout:
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#ifdef CONFIG_SMP
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leave_critical_section(flags);
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#endif
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return ret;
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}
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/****************************************************************************
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* Name: mm_takesemaphore
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*
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* Description:
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* Take the MM mutex. This is the normal action before all memory
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* management actions.
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*
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****************************************************************************/
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void mm_takesemaphore(FAR struct mm_heap_s *heap)
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{
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#ifdef CONFIG_SMP
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irqstate_t flags = enter_critical_section();
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#endif
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pid_t my_pid = getpid();
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/* Does the current task already hold the semaphore? */
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if (heap->mm_holder == my_pid)
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{
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/* Yes, just increment the number of references held by the current
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* task.
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*/
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heap->mm_counts_held++;
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}
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else
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{
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int ret;
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/* Take the semaphore (perhaps waiting) */
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mseminfo("PID=%d taking\n", my_pid);
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do
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{
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ret = _SEM_WAIT(&heap->mm_semaphore);
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/* The only case that an error should occur here is if the wait
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* was awakened by a signal.
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*/
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if (ret < 0)
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{
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#if defined(CONFIG_BUILD_FLAT) || defined(__KERNEL__)
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DEBUGASSERT(ret == -EINTR || ret == -ECANCELED);
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#else
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int errcode = get_errno();
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DEBUGASSERT(errcode == EINTR || errcode == ECANCELED);
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ret = -errcode;
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#endif
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}
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}
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while (ret == -EINTR);
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/* We have it (or some awful, unexpected error occurred). Claim
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* the semaphore for the current task and return.
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*/
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heap->mm_holder = my_pid;
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heap->mm_counts_held = 1;
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}
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#ifdef CONFIG_SMP
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leave_critical_section(flags);
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#endif
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mseminfo("Holder=%d count=%d\n", heap->mm_holder, heap->mm_counts_held);
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}
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/****************************************************************************
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* Name: mm_givesemaphore
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*
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* Description:
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* Release the MM mutex when it is not longer needed.
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*
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****************************************************************************/
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void mm_givesemaphore(FAR struct mm_heap_s *heap)
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{
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#ifdef CONFIG_SMP
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irqstate_t flags = enter_critical_section();
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#endif
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#if defined(CONFIG_DEBUG_ASSERTIONS) || \
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(defined(MONITOR_MM_SEMAPHORE) && defined(CONFIG_DEBUG_INFO))
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pid_t my_pid = getpid();
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#endif
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/* The current task should be holding at least one reference to the
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* semaphore.
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*/
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DEBUGASSERT(heap->mm_holder == my_pid);
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/* Does the current task hold multiple references to the semaphore */
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if (heap->mm_counts_held > 1)
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{
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/* Yes, just release one count and return */
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heap->mm_counts_held--;
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mseminfo("Holder=%d count=%d\n", heap->mm_holder,
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heap->mm_counts_held);
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}
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else
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{
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/* Nope, this is the last reference held by the current task. */
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mseminfo("PID=%d giving\n", my_pid);
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heap->mm_holder = NO_HOLDER;
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heap->mm_counts_held = 0;
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DEBUGVERIFY(_SEM_POST(&heap->mm_semaphore));
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}
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#ifdef CONFIG_SMP
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leave_critical_section(flags);
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#endif
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}
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