问题
I am mmapping a block as:
mapAddr = mmap((void*) 0, curMapSize, PROT_NONE, MAP_LOCKED|MAP_SHARED, fd, curMapOffset);
if this does not fail (mapAddr != MAP_FAILED) I query mincore as:
err = mincore((char*) mapAddr, pageSize, &mincoreRet);
to find out whether it is in RAM. In case it is in RAM (err == 0 && mincoreRet & 0x01) I mmap it again for reading as:
copyAddr = mmap((void*) 0, curMapSize, PROT_READ, MAP_LOCKED|MAP_SHARED, fd, curMapOffset);
and then I try to copy it out to my buffer as:
memcpy(data, copyAddr, pageSize);
everything works fine except in the last memcpy once in a while I get SIGBUS. When I check /proc/ /smaps at the time of the failure I notice that it has Rss as well as Locked fields as 0 as listed below:
7f4a4c118000-7f4a4c119000 r--s 00326000 00:17 6 <file name>
Size: 4 kB
Rss: 0 kB
Pss: 0 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Referenced: 0 kB
Anonymous: 0 kB
AnonHugePages: 0 kB
Swap: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Locked: 0 kB
Any thoughts? This is happening on ubuntu 12.0.4 with kernel version 3.5.0-36.
来源：https://stackoverflow.com/questions/21230720/sigbus-while-doing-memcpy-from-mmap-ed-buffer-which-is-in-ram-as-identified-by-m