Begin implementation of using memory-mapped files for shared memory

svn path=/trunk/boinc/; revision=13467

api/boinc_api.C

@@ -167,12 +167,21 @@ static int setup_shared_mem() {
         delete app_client_shm;
         app_client_shm = NULL;
     }
+#else
+#ifdef USE_FILE_MAPPED_SHMEM
+    if (create_shmem(
+            MMAPPED_FILE_NAME, sizeof(SHARED_MEM), (void**)&app_client_shm->shm
+        )) {
+        delete app_client_shm;
+        app_client_shm = NULL;
+    }
 #else
     if (attach_shmem(aid.shmem_seg_name, (void**)&app_client_shm->shm)) {
         delete app_client_shm;
         app_client_shm = NULL;
     }
-#endif
+#endif  // ! USE_FILE_MAPPED_SHMEM
+#endif  // ! _WIN32
     if (app_client_shm == NULL) return -1;
     return 0;
 }

api/graphics2.h

@@ -17,7 +17,12 @@ extern void boinc_app_key_release(int, int);
 //
 extern void boinc_graphics_loop(int, char**);
 extern void* boinc_graphics_make_shmem(char*, int);
+
+#ifdef USE_FILE_MAPPED_SHMEM
+// Use boinc_graphics_make_shmem() instead of boinc_graphics_get_shmem()
+#else
 extern void* boinc_graphics_get_shmem(char*);
+#endif
 
 // Implementation stuff
 //

api/graphics2_util.C

@@ -35,15 +35,19 @@ void* boinc_graphics_make_shmem(char* prog_name, int size) {
     return p;
 #else
     void* p;
+#ifdef USE_FILE_MAPPED_SHMEM
+    int retval = create_shmem("gfx_mmap_file", size, &p);
+#else
     key_t key = get_shmem_name(prog_name);
     int retval = create_shmem(key, size, 0, &p);
+#endif
     if (retval) return 0;
     return p;
 #endif
 }
 
-void* boinc_graphics_get_shmem(char* prog_name) {
 #ifdef _WIN32
+void* boinc_graphics_get_shmem(char* prog_name) {
     HANDLE shmem_handle;
     char shmem_name[256];
     void* p;
@@ -51,11 +55,17 @@ void* boinc_graphics_get_shmem(char* prog_name) {
     shmem_handle = attach_shmem(shmem_name, &p);
     if (shmem_handle == NULL) return 0;
     return p;
+}
 #else
+#ifdef USE_FILE_MAPPED_SHMEM
+// Use boinc_graphics_make_shmem() instead of boinc_graphics_get_shmem()
+#else
+void* boinc_graphics_get_shmem(char* prog_name) {
     void* p;
     key_t key = get_shmem_name(prog_name);
     int retval = attach_shmem(key, &p);
     if (retval) return 0;
     return p;
-#endif
 }
+#endif
+#endif

checkin_notes

@@ -8135,3 +8135,22 @@ Rytis   26 Aug 2007
     html/
         inc/util.inc
         user/team_email_list.php
+
+Charlie 25 Aug 2007
+    Begin implementation of using memory-mapped files for shared memory.
+    As a temporary measure during development, the new shared memory logic 
+    is selected by defining USE_FILE_MAPPED_SHMEM.  Once the conversion is 
+    complete, we will use these as guideposts to remove the old logic 
+    (using shmget,shmat, shmdt, shmctl, key_t, etc.) and then remove the 
+    references to USE_FILE_MAPPED_SHMEM.
+    Note: these changes are to the HEAD / trunk only, for version 6.
+    
+    api/
+        boinc_api.C
+        graphics2.h
+        graphics2_util.C
+    client/
+        app.C
+        app_start.C
+    lib/
+        shmem.C,h

client/app.C

@@ -184,7 +184,11 @@ void ACTIVE_TASK::cleanup_task() {
     int retval;
 
     if (app_client_shm.shm) {
+#ifdef USE_FILE_MAPPED_SHMEM
+        retval = detach_shmem(app_client_shm.shm, sizeof(SHARED_MEM));
+#else
         retval = detach_shmem(app_client_shm.shm);
+ #endif
         if (retval) {
             msg_printf(NULL, MSG_INTERNAL_ERROR,
                 "Couldn't detach shared memory: %s", boincerror(retval)

client/app_start.C

@@ -575,10 +575,17 @@ int ACTIVE_TASK::start(bool first_time) {
     // Set up core/app shared memory seg if needed
     //
     if (!app_client_shm.shm) {
+#ifdef USE_FILE_MAPPED_SHMEM
+        sprintf(buf, "%s%s", slot_dir, MMAPPED_FILE_NAME);
+        retval = create_shmem(
+            buf, sizeof(SHARED_MEM), (void**)&app_client_shm.shm
+        );
+#else
         retval = create_shmem(
             shmem_seg_name, sizeof(SHARED_MEM), gstate.boinc_project_gid,
             (void**)&app_client_shm.shm
         );
+#endif
         if (retval) {
             needs_shmem = true;
             destroy_shmem(shmem_seg_name);  // Don't leave an orphan shmem segment

lib/shmem.C

@@ -48,6 +48,12 @@ extern "C" int debug_printf(const char *fmt, ...);
 #endif
 #endif
 
+#ifdef USE_FILE_MAPPED_SHMEM
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#endif
+
 #include "error_numbers.h"
 #include "shmem.h"
 
@@ -159,6 +165,50 @@ int detach_shmem(void* p) {
 
 #else
 
+#ifdef USE_FILE_MAPPED_SHMEM
+
+int create_shmem(char *path, size_t size, void** pp) {
+    int fd;
+    
+    // try 0666, then SHM_R|SHM_W
+    // seems like some platforms require one or the other
+    // (this may be superstition)
+    //
+    // NOTE: in principle it should be 0660, not 0666
+    // (i.e. Apache should belong to the same group as the
+    // project admin user, and should therefore be able to access the seg.
+    // However, this doesn't seem to work on some Linux systems.
+    // I don't have time to figure this out (31 July 07)
+    // it's a big headache for anyone it affects,
+    // and it's not a significant security issue.
+    //
+    fd = open(path, O_RDWR | O_CREAT, 0666);
+    if (fd < 0)
+        return ERR_SHMGET;
+
+    *pp = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_FILE | MAP_SHARED, fd, 0);
+    
+    // Now close the file. The kernel doesnÕt use our file descriptor.
+    close(fd);
+
+    if (*pp == MAP_FAILED)
+        return ERR_SHMGET;
+
+    return 0;
+}
+
+int destroy_shmem(key_t key){
+    return 0;
+}
+
+int detach_shmem(void* p, size_t size) {
+    int retval;
+    retval = shmdt((char *)p);
+    return retval;
+}
+
+#else   // USE_FILE_MAPPED_SHMEM
+
 int create_shmem(key_t key, int size, gid_t gid, void** pp) {
     int id;
     
@@ -272,12 +322,15 @@ int print_shmem_info(key_t key) {
     return 0;
 }
 
+#endif  // USE_FILE_MAPPED_SHMEM
+
 // For debugging shared memory logic
 // For testing on Apple, Linux, UNIX systems with limited number 
 // of shared memory segments per process and / or system-wide
 // Mac OS X has a default limit of 8 segments per process, 32 system-wide
 // If 
 void stress_shmem(short reduce_by) {
+#ifndef USE_FILE_MAPPED_SHMEM
     int retval;
     void * shmaddr[16];
     key_t key[] = {
@@ -297,8 +350,9 @@ void stress_shmem(short reduce_by) {
             retval = shmctl(id, IPC_RMID, 0);
         }
     }
+#endif  // !defined(USE_FILE_MAPPED_SHMEM)
 }
 
-#endif
+#endif  // !defined(_WIN32) && !defined(__EMX__)
 
 const char *BOINC_RCSID_f835f078de = "$Id$";

lib/shmem.h

@@ -44,16 +44,24 @@ int detach_shmem(HANDLE hSharedMem, void* p);
 
 #else
 
+#ifdef USE_FILE_MAPPED_SHMEM
+
+#define MMAPPED_FILE_NAME    "boinc_mmap_file"
+
+// create a shared-memory segment of the given size.
+//
+extern int create_shmem(char *path, size_t size, void** pp);
+
+// detach from a shared-mem segment
+//
+extern int detach_shmem(void* p, size_t size);
+
+#else
+
 // create a shared-memory segment of the given size.
 //
 extern int create_shmem(key_t, int size, gid_t gid, void**);
 
-// Destroy a shared-memory segment.
-// If there are attachments to it,
-// print a message in a loop until the attachments are gone
-//
-extern int destroy_shmem(key_t);
-
 // attach to a shared-memory segment
 //
 extern int attach_shmem(key_t, void**);
@@ -64,11 +72,19 @@ extern int detach_shmem(void*);
 
 extern int shmem_info(key_t key);
 
+#endif
+
+// Destroy a shared-memory segment.
+// If there are attachments to it,
+// print a message in a loop until the attachments are gone
+//
+extern int destroy_shmem(key_t);
+
 #ifndef __EMX__
 // For testing on Apple, Linux, UNIX systems with limited number 
 // of shared memory segments per process and / or system-wide
 void stress_shmem(short reduce_by);
 #endif
 
-#endif
-#endif
+#endif      // !defined(_WIN32)
+#endif      // BOINC_SHMEM_H