shmem.h

   1 /*
   2  * shmem.h
   3  *
   4  *  Created on: Aug 13, 2009
   5  *      Author: Ben Langmead
   6  */
   7
   8 #ifndef SHMEM_H_
   9 #define SHMEM_H_
  10
  11 #ifdef BOWTIE_SHARED_MEM
  12
  13 #include <string>
  14 #include <sys/shm.h>
  15 #include <unistd.h>
  16 #include <sys/shm.h>
  17 #include <errno.h>
  18 #include <stdint.h>
  19 #include <stdexcept>
  20 #include "str_util.h"
  21
  22 extern void notifySharedMem(void *mem, size_t len);
  23
  24 extern void waitSharedMem(void *mem, size_t len);
  25
  26 #define ALLOC_SHARED_U8 allocSharedMem<uint8_t>
  27 #define ALLOC_SHARED_U32 allocSharedMem<uint32_t>
  28 #define FREE_SHARED shmdt
  29 #define NOTIFY_SHARED notifySharedMem
  30 #define WAIT_SHARED waitSharedMem
  31
  32 #define SHMEM_UNINIT  0xafba4242
  33 #define SHMEM_INIT    0xffaa6161
  34
  35 /**
  36  * Tries to allocate a shared-memory chunk for a given file of a given size.
  37  */
  38 template <typename T>
  39 bool allocSharedMem(std::string fname,
  40                     size_t len,
  41                     T ** dst,
  42                     const char *memName,
  43                     bool verbose)
  44 {
  45         using namespace std;
  46         int shmid = -1;
  47         // Calculate key given string
  48         key_t key = (key_t)hash_string(fname);
  49         shmid_ds ds;
  50         int ret;
  51         // Reserve 4 bytes at the end for silly synchronization
  52         size_t shmemLen = len + 4;
  53         if(verbose) {
  54                 cerr << "Reading " << len << "+4 bytes into shared memory for " << memName << endl;
  55         }
  56         T *ptr = NULL;
  57         while(true) {
  58                 // Create the shrared-memory block
  59                 if((shmid = shmget(key, shmemLen, IPC_CREAT | 0666)) < 0) {
  60                         if(errno == ENOMEM) {
  61                                 cerr << "Out of memory allocating shared area " << memName << endl;
  62                         } else if(errno == EACCES) {
  63                                 cerr << "EACCES" << endl;
  64                         } else if(errno == EEXIST) {
  65                                 cerr << "EEXIST" << endl;
  66                         } else if(errno == EINVAL) {
  67                                 cerr << "Warning: shared-memory chunk's segment size doesn't match expected size (" << (shmemLen) << ")" << endl
  68                                          << "Deleteing old shared memory block and trying again." << endl;
  69                                 shmid = shmget(key, 0, 0);
  70                                 if((ret = shmctl(shmid, IPC_RMID, &ds)) < 0) {
  71                                         cerr << "shmctl returned " << ret
  72                                                  << " for IPC_RMID, errno is " << errno
  73                                                  << ", shmid is " << shmid << endl;
  74                                         throw 1;
  75                                 } else {
  76                                         cerr << "Deleted shared mem chunk with shmid " << shmid << endl;
  77                                 }
  78                                 continue;
  79                         } else if(errno == ENOENT) {
  80                                 cerr << "ENOENT" << endl;
  81                         } else if(errno == ENOSPC) {
  82                                 cerr << "ENOSPC" << endl;
  83                         } else {
  84                                 cerr << "shmget returned " << shmid << " for and errno is " << errno << endl;
  85                         }
  86                         throw 1;
  87                 }
  88                 ptr = (T*)shmat(shmid, 0, 0);
  89                 if(ptr == (void*)-1) {
  90                         cerr << "Failed to attach " << memName << " to shared memory with shmat()." << endl;
  91                         throw 1;
  92                 }
  93                 if(ptr == NULL) {
  94                         cerr << memName << " pointer returned by shmat() was NULL." << endl;
  95                         throw 1;
  96                 }
  97                 // Did I create it, or did I just attach to one created by
  98                 // another process?
  99                 if((ret = shmctl(shmid, IPC_STAT, &ds)) < 0) {
 100                         cerr << "shmctl returned " << ret << " for IPC_STAT and errno is " << errno << endl;
 101                         throw 1;
 102                 }
 103                 if(ds.shm_segsz != shmemLen) {
 104                         cerr << "Warning: shared-memory chunk's segment size (" << ds.shm_segsz
 105                                  << ") doesn't match expected size (" << shmemLen << ")" << endl
 106                                  << "Deleteing old shared memory block and trying again." << endl;
 107                         if((ret = shmctl(shmid, IPC_RMID, &ds)) < 0) {
 108                                 cerr << "shmctl returned " << ret << " for IPC_RMID and errno is " << errno << endl;
 109                                 throw 1;
 110                         }
 111                 } else {
 112                         break;
 113                 }
 114         } // while(true)
 115         *dst = ptr;
 116         bool initid = (((volatile uint32_t*)((char*)ptr + len))[0] == SHMEM_INIT);
 117         if(ds.shm_cpid == getpid() && !initid) {
 118                 if(verbose) {
 119                         cerr << "  I (pid = " << getpid() << ") created the "
 120                              << "shared memory for " << memName << endl;
 121                 }
 122                 // Set this value just off the end of the chunk to
 123                 // indicate that the data hasn't been read yet.
 124                 ((volatile uint32_t*)((char*)ptr + len))[0] = SHMEM_UNINIT;
 125                 return true;
 126         } else {
 127                 if(verbose) {
 128                         cerr << "  I (pid = " << getpid()
 129                              << ") did not create the shared memory for "
 130                              << memName << ".  Pid " << ds.shm_cpid << " did." << endl;
 131                 }
 132                 return false;
 133         }
 134 }
 135
 136 #else
 137
 138 #define ALLOC_SHARED_U8(...) 0
 139 #define ALLOC_SHARED_U32(...) 0
 140 #define FREE_SHARED(...)
 141 #define NOTIFY_SHARED(...)
 142 #define WAIT_SHARED(...)
 143
 144 #endif /*BOWTIE_SHARED_MEM*/
 145
 146 #endif /* SHMEM_H_ */