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Fix mdb_reader_pid().

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Treat unexpected errors as "don't know".  Invert Pidcheck return
value, so nonzero including error codes = "the process may exist".

On Windows: Catch exited but still existing processes.  Handle
undefined PROCESS_QUERY_LIMITED_INFORMATION.
On Unix: don't trust F_GETLK error to leave the input alone,
the fcntl() doc seems unclear.
This commit is contained in:
Hallvard Furuseth 2013-08-08 19:43:04 +02:00
parent 636c2d2a29
commit 1878213092
1 changed files with 34 additions and 24 deletions
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58
libraries/liblmdb/mdb.c
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@ -162,6 +162,11 @@
#define GET_PAGESIZE(x) {SYSTEM_INFO si; GetSystemInfo(&si); (x) = si.dwPageSize;}
#define close(fd) (CloseHandle(fd) ? 0 : -1)
#define munmap(ptr,len) UnmapViewOfFile(ptr)
#ifndef PROCESS_QUERY_LIMITED_INFORMATION
#define MDB_PROCESS_QUERY_LIMITED_INFORMATION PROCESS_QUERY_LIMITED_INFORMATION
#else
#define MDB_PROCESS_QUERY_LIMITED_INFORMATION 0x1000
#endif
#define Z "I"
#else
@ -2019,7 +2024,8 @@ enum Pidlock_op {
#endif
/** Set or check a pid lock. Set returns 0 on success.
* Check returns 0 if lock exists (meaning the process is alive).
* Check returns 0 if the process is certainly dead, nonzero if it may
* be alive (the lock exists or an error happened so we do not know).
*
* On Windows Pidset is a no-op, we merely check for the existence
* of the process with the given pid. On POSIX we use a single byte
@ -2029,32 +2035,35 @@ static int
mdb_reader_pid(MDB_env *env, enum Pidlock_op op, pid_t pid)
{
#ifdef _WIN32
int ret = 0;
HANDLE h;
int ver, query;
switch(op) {
case Pidset:
break;
case Pidcheck:
if (op == Pidcheck) {
h = OpenProcess(env->me_pidquery, FALSE, pid);
/* No documented "no such process" code, but other program use this: */
if (!h)
return GetLastError();
return ErrCode() != ERROR_INVALID_PARAMETER;
/* A process exists until all handles to it close. Has it exited? */
ret = WaitForSingleObject(h, 0) != 0;
CloseHandle(h);
break;
}
return 0;
return ret;
#else
int rc;
struct flock lock_info;
memset((void *)&lock_info, 0, sizeof(lock_info));
lock_info.l_type = F_WRLCK;
lock_info.l_whence = SEEK_SET;
lock_info.l_start = pid;
lock_info.l_len = 1;
while ((rc = fcntl(env->me_lfd, op, &lock_info)) &&
(rc = ErrCode()) == EINTR) ;
if (op == F_GETLK && rc == 0 && lock_info.l_type == F_UNLCK)
rc = -1;
return rc;
for (;;) {
int rc;
struct flock lock_info;
memset(&lock_info, 0, sizeof(lock_info));
lock_info.l_type = F_WRLCK;
lock_info.l_whence = SEEK_SET;
lock_info.l_start = pid;
lock_info.l_len = 1;
if ((rc = fcntl(env->me_lfd, op, &lock_info)) == 0) {
if (op == F_GETLK && lock_info.l_type != F_UNLCK)
rc = -1;
} else if ((rc = ErrCode()) == EINTR) {
continue;
}
return rc;
}
#endif
}
@ -3247,7 +3256,7 @@ mdb_env_open2(MDB_env *env)
/* See if we should use QueryLimited */
rc = GetVersion();
if ((rc & 0xff) > 5)
env->me_pidquery = PROCESS_QUERY_LIMITED_INFORMATION;
env->me_pidquery = MDB_PROCESS_QUERY_LIMITED_INFORMATION;
else
env->me_pidquery = PROCESS_QUERY_INFORMATION;
@ -8144,9 +8153,10 @@ int mdb_reader_check(MDB_env *env, int *dead)
if (mr[i].mr_pid && mr[i].mr_pid != env->me_pid) {
pid = mr[i].mr_pid;
if (mdb_pid_insert(pids, pid) == 0) {
if (mdb_reader_pid(env, Pidcheck, pid)) {
if (!mdb_reader_pid(env, Pidcheck, pid)) {
LOCK_MUTEX_R(env);
if (mdb_reader_pid(env, Pidcheck, pid)) {
/* Recheck, a new process may have reused pid */
if (!mdb_reader_pid(env, Pidcheck, pid)) {
for (j=i; j<rdrs; j++)
if (mr[j].mr_pid == pid) {
mr[j].mr_pid = 0;