Re: [PATCH v6 00/16] daemon-win32

[Pat Thoyts <patthoyts@users.sourceforge.net>]

Erik Faye-Lund <kusmabite@gmail.com> writes:

>On Thu, Nov 4, 2010 at 1:28 AM, Pat Thoyts
><patthoyts@users.sourceforge.net> wrote:
>> Erik Faye-Lund <kusmabite@gmail.com> writes:
>>>On Wed, Nov 3, 2010 at 11:18 PM, Erik Faye-Lund <kusmabite@gmail.com> wrote:
>>>> diff --git a/compat/mingw.c b/compat/mingw.c
>>>> index b780200..47e7d26 100644
>>>> --- a/compat/mingw.c
>>>> +++ b/compat/mingw.c
>>>> @@ -1519,8 +1519,10 @@ pid_t waitpid(pid_t pid, int *status, unsigned options)
>>>>        }
>>>>
>>>>        if (pid > 0 && options & WNOHANG) {
>>>> -               if (WAIT_OBJECT_0 != WaitForSingleObject((HANDLE)pid, 0))
>>>> +               if (WAIT_OBJECT_0 != WaitForSingleObject((HANDLE)pid, 0)) {
>>>
>>>AAAND the last one is right here as well:
>>>-              if (WAIT_OBJECT_0 != WaitForSingleObject((HANDLE)pid, 0))
>>>+              if (WAIT_OBJECT_0 != WaitForSingleObject(h, 0)) {
>>>
>>
>> Applying both of these doesn't fix the handle leak when I test
>> this. Looking further I believe it is due to the use of a reallocated
>> array. When you remove a pinfo structure you realloc to the one you
>> found, potentially freeing items you still require.
>>
>
>If this is the reason, then that's a bug. The code TRIES to do the
>right thing by memmove'ing the the entro to be deleted to the end.
>Looking over the code, I still don't see anyhing obviously wrong.
>But...
>
>> Attached is a patch that switches to a linked list for this
>> instead. Using this I no longer accumulate leaked handles.
>>
>> ----
>> From e0c05f8f9ed8729648eea92cf654f357fa884e40 Mon Sep 17 00:00:00 2001
>> From: Pat Thoyts <patthoyts@users.sourceforge.net>
>> Date: Thu, 4 Nov 2010 00:23:08 +0000
>> Subject: [PATCH] win32-daemon: fix handle leaks
>>
>> The use of an array of pinfo structures and the realloc used when cleaning
>> up a closed child can free structures that are still in use. Use a linked
>> list instead.
>> This stops the leaking of handles in the win32-daemon.
>>
>> Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>
>> ---
>>  compat/mingw.c |   43 ++++++++++++++++++++++++-------------------
>>  1 files changed, 24 insertions(+), 19 deletions(-)
>>
>> diff --git a/compat/mingw.c b/compat/mingw.c
>> index b780200..29f4036 100644
>> --- a/compat/mingw.c
>> +++ b/compat/mingw.c
>> @@ -637,11 +637,12 @@ static int env_compare(const void *a, const void *b)
>>        return strcasecmp(*ea, *eb);
>>  }
>>
>> -struct {
>> +struct pinfo_t {
>> +       struct pinfo_t *next;
>>        pid_t pid;
>>        HANDLE proc;
>> -} *pinfo;
>> -static int num_pinfo;
>> +} pinfo_t;
>> +struct pinfo_t *pinfo = NULL;
>>  CRITICAL_SECTION pinfo_cs;
>>
>>  static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **env,
>> @@ -746,10 +747,13 @@ static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **env,
>>         * Keep the handle in a list for waitpid.
>>         */
>>        EnterCriticalSection(&pinfo_cs);
>> -       num_pinfo++;
>> -       pinfo = xrealloc(pinfo, sizeof(*pinfo) * num_pinfo);
>> -       pinfo[num_pinfo - 1].pid = pi.dwProcessId;
>> -       pinfo[num_pinfo - 1].proc = pi.hProcess;
>> +       {
>> +               struct pinfo_t *info = xmalloc(sizeof(struct pinfo_t));
>> +               info->pid = pi.dwProcessId;
>> +               info->proc = pi.hProcess;
>> +               info->next = pinfo;
>> +               pinfo = info;
>> +       }
>>        LeaveCriticalSection(&pinfo_cs);
>>
>>        return (pid_t)pi.dwProcessId;
>> @@ -1519,13 +1523,15 @@ pid_t waitpid(pid_t pid, int *status, unsigned options)
>>        }
>>
>>        if (pid > 0 && options & WNOHANG) {
>> -               if (WAIT_OBJECT_0 != WaitForSingleObject((HANDLE)pid, 0))
>> +               if (WAIT_OBJECT_0 != WaitForSingleObject(h, 0)) {
>> +                       CloseHandle(h);
>>                        return 0;
>> +               }
>>                options &= ~WNOHANG;
>>        }
>>
>>        if (options == 0) {
>> -               int i;
>> +               struct pinfo_t **ppinfo;
>>                if (WaitForSingleObject(h, INFINITE) != WAIT_OBJECT_0) {
>>                        CloseHandle(h);
>>                        return 0;
>> @@ -1536,17 +1542,16 @@ pid_t waitpid(pid_t pid, int *status, unsigned options)
>>
>>                EnterCriticalSection(&pinfo_cs);
>>
>> -               for (i = 0; i < num_pinfo; ++i)
>> -                       if (pinfo[i].pid == pid)
>> +               ppinfo = &pinfo;
>> +               while (*ppinfo) {
>> +                       struct pinfo_t *info = *ppinfo;
>> +                       if (info->pid == pid) {
>> +                               CloseHandle(info->proc);
>> +                               *ppinfo = info->next;
>> +                               free(info);
>>                                break;
>> -
>> -               if (i < num_pinfo) {
>> -                       CloseHandle(pinfo[i].proc);
>> -                       memmove(pinfo + i, pinfo + i + 1,
>> -                           sizeof(*pinfo) * (num_pinfo - i - 1));
>> -                       num_pinfo--;
>> -                       pinfo = xrealloc(pinfo,
>> -                           sizeof(*pinfo) * num_pinfo);
>> +                       }
>> +                       ppinfo = &info->next;
>>                }
>>
>>                LeaveCriticalSection(&pinfo_cs);
>
>...yeah, using a linked list is more elegant. Do you mind if I snatch
>your code and leave a comment in the commit message?
>

Sure. When I wrote the comment I'd forgotten about the memmove. So
hmmm. However, I just pulled you win32-daemon branch and applied this
patch on top. Now there are no more warnings so your union fix is
good. As I understand it thats the way to handle this particular
warning. ipv6 and ipv4 both still work fine as well.

With my patch a while true; do git ls-remote; done shows no more leaking
handles or memory. So the use of a list is fixing something. Looking
great now.

-- 
Pat Thoyts                            http://www.patthoyts.tk/
PGP fingerprint 2C 6E 98 07 2C 59 C8 97  10 CE 11 E6 04 E0 B9 DD