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* Automatically recover the database in case of a crash.

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This commit is contained in:
Eelco Dolstra 2003-10-14 15:33:00 +00:00
parent 1d61e473c8
commit c190f051ac
6 changed files with 204 additions and 41 deletions
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41
src/pathlocks.cc
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@ -1,10 +1,39 @@
#include <cerrno>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "pathlocks.hh"
bool lockFile(int fd, LockType lockType, bool wait)
{
struct flock lock;
if (lockType == ltRead) lock.l_type = F_RDLCK;
else if (lockType == ltWrite) lock.l_type = F_WRLCK;
else if (lockType == ltNone) lock.l_type = F_UNLCK;
else abort();
lock.l_whence = SEEK_SET;
lock.l_start = 0;
lock.l_len = 0; /* entire file */
if (wait) {
while (fcntl(fd, F_SETLKW, &lock) != 0)
if (errno != EINTR)
throw SysError(format("acquiring/releasing lock"));
} else {
while (fcntl(fd, F_SETLK, &lock) != 0) {
if (errno == EACCES || errno == EAGAIN) return false;
if (errno != EINTR)
throw SysError(format("acquiring/releasing lock"));
}
}
return true;
}
/* This enables us to check whether are not already holding a lock on
a file ourselves. POSIX locks (fcntl) suck in this respect: if we
close a descriptor, the previous lock will be closed as well. And
@ -43,16 +72,8 @@ PathLocks::PathLocks(const PathSet & _paths)
fds.push_back(fd);
this->paths.push_back(lockPath);
/* Lock it. */
struct flock lock;
lock.l_type = F_WRLCK; /* exclusive lock */
lock.l_whence = SEEK_SET;
lock.l_start = 0;
lock.l_len = 0; /* entire file */
while (fcntl(fd, F_SETLKW, &lock) == -1)
if (errno != EINTR)
throw SysError(format("acquiring lock on `%1%'") % lockPath);
/* Acquire an exclusive lock. */
lockFile(fd, ltWrite, true);
lockedPaths.insert(lockPath);
}