[PATCH 4/3] http: check curl_multi_remove_handle error code

[Eric Wong]

Junio C Hamano <gits...@pobox.com> wrote:
> Eric Wong <e...@80x24.org> writes:
> > The key patch here is 3/3 which seems like an obvious fix to
> > adding the problem of adding a curl easy handle to a curl multi
> > handle repeatedly.
> 
> Yeah, sounds like the right thing to do and 2/3 makes it really easy
> to read the resulting code.
> 
> > I will investigate those failures in a week or two when I regain
> > regular computer access.
> 
> Thanks. Will tentatively queue on 'pu' and wait for updates.

I'm comfortable with the original 3 patch series in 'next'
and being merged to 'master' and 'maint', soon.

I don't think the following 4/3 is strictly necessary now, so
I'd be more comfortable with it being tested in 'pu' or 'next'
for a longer period.

(online today, but not much tomorrow or another few days after)

-----------8<-----------
Subject: [PATCH] http: check curl_multi_remove_handle error code

This should help detect bugs in future changes.  While we're at
it, fix a (probably innocuous) bug in our http_cleanup function
for users of older curl.

curl_multi_remove_handle was not idempotent until curl 7.33.0
with commit 84f3b3dd448399f9548468676e1bd1475dba8de5
("curl_multi_remove_handle: allow multiple removes"),
so we track the "curlm" membership of the curl easy handle
ourselves with a new "in_multi" flag.

Tested with curl 7.26.0 and 7.38.0 on Debian 7.x (wheezy) and
Debian 8.x (jessie) respectively.

Signed-off-by: Eric Wong <e...@80x24.org>
---
 http.c | 12 ++++++++++--
 http.h |  1 +
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/http.c b/http.c
index 82ed542..9f97749 100644
--- a/http.c
+++ b/http.c
@@ -204,7 +204,12 @@ static void finish_active_slot(struct active_request_slot 
*slot)
 static void xmulti_remove_handle(struct active_request_slot *slot)
 {
 #ifdef USE_CURL_MULTI
-       curl_multi_remove_handle(curlm, slot->curl);
+       CURLMcode code = curl_multi_remove_handle(curlm, slot->curl);
+
+       if (code != CURLM_OK)
+               die("curl_multi_remove_handle failed (%p): %s",
+                       slot->curl, curl_multi_strerror(code));
+       slot->in_multi = 0;
 #endif
 }
 
@@ -888,7 +893,8 @@ void http_cleanup(void)
        while (slot != NULL) {
                struct active_request_slot *next = slot->next;
                if (slot->curl != NULL) {
-                       xmulti_remove_handle(slot);
+                       if (slot->in_multi)
+                               xmulti_remove_handle(slot);
                        curl_easy_cleanup(slot->curl);
                }
                free(slot);
@@ -965,6 +971,7 @@ struct active_request_slot *get_active_slot(void)
                newslot = xmalloc(sizeof(*newslot));
                newslot->curl = NULL;
                newslot->in_use = 0;
+               newslot->in_multi = 0;
                newslot->next = NULL;
 
                slot = active_queue_head;
@@ -1033,6 +1040,7 @@ int start_active_slot(struct active_request_slot *slot)
                slot->in_use = 0;
                return 0;
        }
+       slot->in_multi = 1;
 
        /*
         * We know there must be something to do, since we just added
diff --git a/http.h b/http.h
index 5ab9d9c..3339d70 100644
--- a/http.h
+++ b/http.h
@@ -60,6 +60,7 @@ struct slot_results {
 struct active_request_slot {
        CURL *curl;
        int in_use;
+       int in_multi;
        CURLcode curl_result;
        long http_code;
        int *finished;
-- 
EW