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From d3036f34cce421990e8268ee4bbfc0d9f5ceb054 Mon Sep 17 00:00:00 2001
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From: Daniel Stenberg <daniel@haxx.se>
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Date: Thu, 13 Jun 2013 19:27:12 +0200
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Subject: [PATCH] curl_easy_perform: avoid busy-looping
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When curl_multi_wait() finds no file descriptor to wait for, it returns
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instantly and this must be handled gracefully within curl_easy_perform()
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or cause a busy-loop. Starting now, repeated fast returns without any
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file descriptors is detected and a gradually increasing sleep will be
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used (up to a max of 1000 milliseconds) before continuing the loop.
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Bug: http://curl.haxx.se/bug/view.cgi?id=1238
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Reported-by: Miguel Angel
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[upstream commit 0feeab7802dd2a6465d22d153d8d36b2cca99b96]
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Signed-off-by: Kamil Dudka <kdudka@redhat.com>
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---
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lib/easy.c | 25 +++++++++++++++++++++++++
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1 files changed, 25 insertions(+), 0 deletions(-)
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diff --git a/lib/easy.c b/lib/easy.c
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index 2739598..a7051dd 100644
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--- a/lib/easy.c
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+++ b/lib/easy.c
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@@ -410,6 +410,9 @@ CURLcode curl_easy_perform(CURL *easy)
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bool done = FALSE;
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int rc;
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struct SessionHandle *data = easy;
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+ int without_fds = 0; /* count number of consecutive returns from
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+ curl_multi_wait() without any filedescriptors */
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+ struct timeval before;
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if(!easy)
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return CURLE_BAD_FUNCTION_ARGUMENT;
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@@ -445,6 +448,7 @@ CURLcode curl_easy_perform(CURL *easy)
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int still_running;
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int ret;
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+ before = curlx_tvnow();
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mcode = curl_multi_wait(multi, NULL, 0, 1000, &ret;;
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if(mcode == CURLM_OK) {
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@@ -453,6 +457,27 @@ CURLcode curl_easy_perform(CURL *easy)
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code = CURLE_RECV_ERROR;
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break;
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}
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+ else if(ret == 0) {
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+ struct timeval after = curlx_tvnow();
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+ /* If it returns without any filedescriptor instantly, we need to
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+ avoid busy-looping during periods where it has nothing particular
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+ to wait for */
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+ if(curlx_tvdiff(after, before) <= 10) {
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+ without_fds++;
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+ if(without_fds > 2) {
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+ int sleep_ms = without_fds * 50;
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+ if(sleep_ms > 1000)
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+ sleep_ms = 1000;
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+ Curl_wait_ms(sleep_ms);
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+ }
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+ }
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+ else
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+ /* it wasn't "instant", restart counter */
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+ without_fds = 0;
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+ }
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+ else
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+ /* got file descriptor, restart counter */
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+ without_fds = 0;
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mcode = curl_multi_perform(multi, &still_running);
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}
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--
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1.7.1
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