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authorDaniel Stenberg <daniel@haxx.se>2019-07-29 13:41:00 +0200
committerDaniel Stenberg <daniel@haxx.se>2019-08-06 09:33:29 +0200
commit02346abc32a3995299fa9c2f35b9f0a1d091b045 (patch)
treede504a328c326fc2ebef7265ddf4de7456fd56be /lib/multi.c
parentcee7639b790f29113759f69c4a955c2ead8bff31 (diff)
downloadcurl-02346abc32a3995299fa9c2f35b9f0a1d091b045.tar.gz
curl_multi_poll: a sister to curl_multi_wait() that waits more
Repeatedly we see problems where using curl_multi_wait() is difficult or just awkward because if it has no file descriptor to wait for internally, it returns immediately and leaves it to the caller to wait for a small amount of time in order to avoid occasional busy-looping. This is often missed or misunderstood, leading to underperforming applications. This change introduces curl_multi_poll() as a replacement drop-in function that accepts the exact same set of arguments. This function works identically to curl_multi_wait() - EXCEPT - for the case when there's nothing to wait for internally, as then this function will by itself wait for a "suitable" short time before it returns. This effectiely avoids all risks of busy-looping and should also make it less likely that apps "over-wait". This also changes the curl tool to use this funtion internally when doing parallel transfers and changes curl_easy_perform() to use it internally. Closes #4163
Diffstat (limited to 'lib/multi.c')
-rwxr-xr-xlib/multi.c40
1 files changed, 28 insertions, 12 deletions
diff --git a/lib/multi.c b/lib/multi.c
index 6e16eafe0..e5c483c56 100755
--- a/lib/multi.c
+++ b/lib/multi.c
@@ -974,12 +974,12 @@ CURLMcode curl_multi_fdset(struct Curl_multi *multi,
#define NUM_POLLS_ON_STACK 10
-CURLMcode Curl_multi_wait(struct Curl_multi *multi,
- struct curl_waitfd extra_fds[],
- unsigned int extra_nfds,
- int timeout_ms,
- int *ret,
- bool *gotsocket) /* if any socket was checked */
+static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
+ struct curl_waitfd extra_fds[],
+ unsigned int extra_nfds,
+ int timeout_ms,
+ int *ret,
+ bool extrawait) /* when no socket, wait */
{
struct Curl_easy *data;
curl_socket_t sockbunch[MAX_SOCKSPEREASYHANDLE];
@@ -993,9 +993,6 @@ CURLMcode Curl_multi_wait(struct Curl_multi *multi,
struct pollfd a_few_on_stack[NUM_POLLS_ON_STACK];
struct pollfd *ufds = &a_few_on_stack[0];
- if(gotsocket)
- *gotsocket = FALSE;
-
if(!GOOD_MULTI_HANDLE(multi))
return CURLM_BAD_HANDLE;
@@ -1124,9 +1121,19 @@ CURLMcode Curl_multi_wait(struct Curl_multi *multi,
free(ufds);
if(ret)
*ret = retcode;
- if(gotsocket && (extra_fds || curlfds))
+ if(!extrawait || extra_fds || curlfds)
/* if any socket was checked */
- *gotsocket = TRUE;
+ ;
+ else {
+ long sleep_ms = 0;
+
+ /* Avoid busy-looping when there's nothing particular to wait for */
+ if(!curl_multi_timeout(multi, &sleep_ms) && sleep_ms) {
+ if(sleep_ms > timeout_ms)
+ sleep_ms = timeout_ms;
+ Curl_wait_ms((int)sleep_ms);
+ }
+ }
return CURLM_OK;
}
@@ -1137,7 +1144,16 @@ CURLMcode curl_multi_wait(struct Curl_multi *multi,
int timeout_ms,
int *ret)
{
- return Curl_multi_wait(multi, extra_fds, extra_nfds, timeout_ms, ret, NULL);
+ return Curl_multi_wait(multi, extra_fds, extra_nfds, timeout_ms, ret, FALSE);
+}
+
+CURLMcode curl_multi_poll(struct Curl_multi *multi,
+ struct curl_waitfd extra_fds[],
+ unsigned int extra_nfds,
+ int timeout_ms,
+ int *ret)
+{
+ return Curl_multi_wait(multi, extra_fds, extra_nfds, timeout_ms, ret, TRUE);
}
/*