鸿蒙源码分析系列篇 https://blog.csdn.net/kuangyufei https://my.oschina.net/u/3751245

kernel/base/vm/los_vm_phys.c

@@ -336,7 +336,7 @@ VOID OsVmPhysPagesFree(LosVmPage *page, UINT8 order)
 
     OsVmPhysFreeListAdd(page, order);//伙伴算法 空闲节点增加
 }
-
+//连续的释放物理页框, 如果8页连在一块是一起释放的,取决于使用了伙伴算法的order
 VOID OsVmPhysPagesFreeContiguous(LosVmPage *page, size_t nPages)
 {
     paddr_t pa;
@@ -551,7 +551,7 @@ UINT32 OsVmPagesToOrder(size_t nPages)
 
     return order;
 }
-
+//释放双链表中的所有节点内存,本质是回归到伙伴orderlist中
 size_t LOS_PhysPagesFree(LOS_DL_LIST *list)
 {
     UINT32 intSave;
@@ -564,16 +564,16 @@ size_t LOS_PhysPagesFree(LOS_DL_LIST *list)
         return 0;
     }
 
-    LOS_DL_LIST_FOR_EACH_ENTRY_SAFE(page, nPage, list, LosVmPage, node) {
-        LOS_ListDelete(&page->node);
-        if (LOS_AtomicDecRet(&page->refCounts) <= 0) {
-            seg = &g_vmPhysSeg[page->segID];
-            LOS_SpinLockSave(&seg->freeListLock, &intSave);
-            OsVmPhysPagesFreeContiguous(page, ONE_PAGE);
-            LOS_AtomicSet(&page->refCounts, 0);
-            LOS_SpinUnlockRestore(&seg->freeListLock, intSave);
+    LOS_DL_LIST_FOR_EACH_ENTRY_SAFE(page, nPage, list, LosVmPage, node) {//宏循环
+        LOS_ListDelete(&page->node);//先把自己摘出去
+        if (LOS_AtomicDecRet(&page->refCounts) <= 0) {//无引用
+            seg = &g_vmPhysSeg[page->segID];//获取物理段
+            LOS_SpinLockSave(&seg->freeListLock, &intSave);//锁住freeList
+            OsVmPhysPagesFreeContiguous(page, ONE_PAGE);//连续释放,注意这里的ONE_PAGE其实有误导,让人以为是释放4K,其实是指连续的物理页框,如果3页连在一块是一起释放的.
+            LOS_AtomicSet(&page->refCounts, 0);//引用重置为0
+            LOS_SpinUnlockRestore(&seg->freeListLock, intSave);//恢复锁
         }
-        count++;
+        count++;//继续取下一个node
     }
 
     return count;

kernel/base/vm/shm.c

@@ -144,7 +144,7 @@ INT32 ShmDeinit(VOID)
 
     return 0;
 }
-//设置共享flag
+//给共享段中所有物理页框贴上共享标签
 STATIC inline VOID ShmSetSharedFlag(struct shmIDSource *seg)
 {
     LosVmPage *page = NULL;
@@ -153,7 +153,7 @@ STATIC inline VOID ShmSetSharedFlag(struct shmIDSource *seg)
         OsSetPageShared(page);
     }
 }
-
+//给共享段中所有物理页框撕掉共享标签
 STATIC inline VOID ShmClearSharedFlag(struct shmIDSource *seg)
 {
     LosVmPage *page = NULL;
@@ -210,35 +210,35 @@ STATIC INT32 ShmAllocSeg(key_t key, size_t size, int shmflg)
     seg->ds.shm_perm.mode = (unsigned int)shmflg & ACCESSPERMS;
     seg->ds.shm_perm.key = key;
     seg->ds.shm_segsz = size;
-    seg->ds.shm_perm.cuid = LOS_GetUserID();
-    seg->ds.shm_perm.uid = LOS_GetUserID();
-    seg->ds.shm_perm.cgid = LOS_GetGroupID();
-    seg->ds.shm_perm.gid = LOS_GetGroupID();
+    seg->ds.shm_perm.cuid = LOS_GetUserID();	//设置用户ID
+    seg->ds.shm_perm.uid = LOS_GetUserID();		//设置用户ID
+    seg->ds.shm_perm.cgid = LOS_GetGroupID();	//设置组ID
+    seg->ds.shm_perm.gid = LOS_GetGroupID();	//设置组ID
     seg->ds.shm_lpid = 0;
-    seg->ds.shm_nattch = 0;
-    seg->ds.shm_cpid = LOS_GetCurrProcessID();
+    seg->ds.shm_nattch = 0;						
+    seg->ds.shm_cpid = LOS_GetCurrProcessID();	//获取进程ID
     seg->ds.shm_atime = 0;
     seg->ds.shm_dtime = 0;
     seg->ds.shm_ctime = time(NULL);
 
     return segNum;
 }
-
+//释放seg->node 所占物理页框,seg本身重置
 STATIC INLINE VOID ShmFreeSeg(struct shmIDSource *seg)
 {
     UINT32 count;
 
-    ShmClearSharedFlag(seg);
-    count = LOS_PhysPagesFree(&seg->node);
-    if (count != (seg->ds.shm_segsz >> PAGE_SHIFT)) {
+    ShmClearSharedFlag(seg);//先撕掉 seg->node 中vmpage的共享标签
+    count = LOS_PhysPagesFree(&seg->node);//再挨个删除物理页框
+    if (count != (seg->ds.shm_segsz >> PAGE_SHIFT)) {//异常,必须要一样
         VM_ERR("free physical pages failed, count = %d, size = %d", count, seg->ds.shm_segsz >> PAGE_SHIFT);
         return;
     }
 
-    seg->status = SHM_SEG_FREE;
-    LOS_ListInit(&seg->node);
+    seg->status = SHM_SEG_FREE;//seg恢复自由之身
+    LOS_ListInit(&seg->node);//重置node
 }
-
+//通过key查找 shmId
 STATIC INT32 ShmFindSegByKey(key_t key)
 {
     INT32 i;
@@ -583,15 +583,15 @@ INT32 ShmCtl(INT32 shmid, INT32 cmd, struct shmid_ds *buf)
 {
     struct shmIDSource *seg = NULL;
     INT32 ret = 0;
-    struct shm_info shmInfo;
-    struct ipc_perm shm_perm;
+    struct shm_info shmInfo;//前往查看结构体内容 ..\vendor_hisi_hi3861_hi3861\hi3861\platform\os\Huawei_LiteOS\components\lib\libc\musl\arch\generic\bits\shm.h
+    struct ipc_perm shm_perm;//前往查看结构体内容 ..\vendor_hisi_hi3861_hi3861\hi3861\platform\os\Huawei_LiteOS\components\lib\libc\musl\arch\generic\bits\ipc.h
 
     cmd = ((UINT32)cmd & ~IPC_64);
 
     SYSV_SHM_LOCK();
 
     if ((cmd != IPC_INFO) && (cmd != SHM_INFO)) {
-        seg = ShmFindSeg(shmid);
+        seg = ShmFindSeg(shmid);//通过索引ID找到seg
         if (seg == NULL) {
             SYSV_SHM_UNLOCK();
             return -1;
@@ -664,7 +664,7 @@ INT32 ShmCtl(INT32 shmid, INT32 cmd, struct shmid_ds *buf)
             shmInfo.shm_tot = 0;
             shmInfo.swap_attempts = 0;
             shmInfo.swap_successes = 0;
-            shmInfo.used_ids = ShmSegUsedCount();
+            shmInfo.used_ids = ShmSegUsedCount();//在使用的seg数
             ret = LOS_ArchCopyToUser(buf, &shmInfo, sizeof(struct shm_info));//把内核空间的共享页数据拷贝到用户空间
             if (ret != 0) {
                 ret = EFAULT;