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multi: add curl_multi_wakeup()

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This commit adds curl_multi_wakeup() which was previously in the TODO
list under the curl_multi_unblock name.

On some platforms and with some configurations this feature might not be
available or can fail, in these cases a new error code
(CURLM_WAKEUP_FAILURE) is returned from curl_multi_wakeup().

Fixes #4418
Closes #4608
This commit is contained in:
Gergely Nagy 2019-11-17 15:12:15 +01:00 • committed by Daniel Stenberg
parent 0a65febccf
commit f3c35e371c
No known key found for this signature in database
GPG key ID: 5CC908FDB71E12C2
20 changed files with 684 additions and 17 deletions
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114
lib/multi.c
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@ -46,6 +46,7 @@
#include "connect.h"
#include "http_proxy.h"
#include "http2.h"
#include "socketpair.h"
/* The last 3 #include files should be in this order */
#include "curl_printf.h"
#include "curl_memory.h"
@ -367,6 +368,21 @@ struct Curl_multi *Curl_multi_handle(int hashsize, /* socket hash */
/* -1 means it not set by user, use the default value */
multi->maxconnects = -1;
#ifdef ENABLE_WAKEUP
if(Curl_socketpair(AF_UNIX, SOCK_STREAM, 0, multi->wakeup_pair) < 0) {
multi->wakeup_pair[0] = CURL_SOCKET_BAD;
multi->wakeup_pair[1] = CURL_SOCKET_BAD;
}
else if(curlx_nonblock(multi->wakeup_pair[0], TRUE) < 0 ||
curlx_nonblock(multi->wakeup_pair[1], TRUE) < 0) {
sclose(multi->wakeup_pair[0]);
sclose(multi->wakeup_pair[1]);
multi->wakeup_pair[0] = CURL_SOCKET_BAD;
multi->wakeup_pair[1] = CURL_SOCKET_BAD;
}
#endif
return multi;
error:
@ -1005,7 +1021,8 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
unsigned int extra_nfds,
int timeout_ms,
int *ret,
bool extrawait) /* when no socket, wait */
bool extrawait, /* when no socket, wait */
bool use_wakeup)
{
struct Curl_easy *data;
curl_socket_t sockbunch[MAX_SOCKSPEREASYHANDLE];
@ -1059,6 +1076,12 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
curlfds = nfds; /* number of internal file descriptors */
nfds += extra_nfds; /* add the externally provided ones */
#ifdef ENABLE_WAKEUP
if(use_wakeup && multi->wakeup_pair[0] != CURL_SOCKET_BAD) {
++nfds;
}
#endif
if(nfds > NUM_POLLS_ON_STACK) {
/* 'nfds' is a 32 bit value and 'struct pollfd' is typically 8 bytes
big, so at 2^29 sockets this value might wrap. When a process gets
@ -1117,6 +1140,14 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
++nfds;
}
#ifdef ENABLE_WAKEUP
if(use_wakeup && multi->wakeup_pair[0] != CURL_SOCKET_BAD) {
ufds[nfds].fd = multi->wakeup_pair[0];
ufds[nfds].events = POLLIN;
++nfds;
}
#endif
if(nfds) {
int pollrc;
/* wait... */
@ -1140,6 +1171,29 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
extra_fds[i].revents = mask;
}
#ifdef ENABLE_WAKEUP
if(use_wakeup && multi->wakeup_pair[0] != CURL_SOCKET_BAD) {
if(ufds[curlfds + extra_nfds].revents & POLLIN) {
char buf[64];
while(1) {
/* the reading socket is non-blocking, try to read
data from it until it receives an error (except EINTR).
In normal cases it will get EAGAIN or EWOULDBLOCK
when there is no more data, breaking the loop. */
if(sread(multi->wakeup_pair[0], buf, sizeof(buf)) < 0) {
#ifndef USE_WINSOCK
if(EINTR == SOCKERRNO)
continue;
#endif
break;
}
}
/* do not count the wakeup socket into the returned value */
retcode--;
}
}
#endif
}
}
@ -1174,7 +1228,8 @@ 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, FALSE);
return Curl_multi_wait(multi, extra_fds, extra_nfds, timeout_ms, ret, FALSE,
FALSE);
}
CURLMcode curl_multi_poll(struct Curl_multi *multi,
@ -1183,7 +1238,55 @@ CURLMcode curl_multi_poll(struct Curl_multi *multi,
int timeout_ms,
int *ret)
{
return Curl_multi_wait(multi, extra_fds, extra_nfds, timeout_ms, ret, TRUE);
return Curl_multi_wait(multi, extra_fds, extra_nfds, timeout_ms, ret, TRUE,
TRUE);
}
CURLMcode curl_multi_wakeup(struct Curl_multi *multi)
{
/* this function is usually called from another thread,
it has to be careful only to access parts of the
Curl_multi struct that are constant */
/* GOOD_MULTI_HANDLE can be safely called */
if(!GOOD_MULTI_HANDLE(multi))
return CURLM_BAD_HANDLE;
#ifdef ENABLE_WAKEUP
/* the wakeup_pair variable is only written during init and cleanup,
making it safe to access from another thread after the init part
and before cleanup */
if(multi->wakeup_pair[1] != CURL_SOCKET_BAD) {
char buf[1];
buf[0] = 1;
while(1) {
/* swrite() is not thread-safe in general, because concurrent calls
can have their messages interleaved, but in this case the content
of the messages does not matter, which makes it ok to call.
The write socket is set to non-blocking, this way this function
cannot block, making it safe to call even from the same thread
that will call Curl_multi_wait(). If swrite() returns that it
would block, it's considered successful because it means that
previous calls to this function will wake up the poll(). */
if(swrite(multi->wakeup_pair[1], buf, sizeof(buf)) < 0) {
int err = SOCKERRNO;
int return_success;
#ifdef USE_WINSOCK
return_success = WSAEWOULDBLOCK == err;
#else
if(EINTR == err)
continue;
return_success = EWOULDBLOCK == err || EAGAIN == err;
#endif
if(!return_success)
return CURLM_WAKEUP_FAILURE;
}
return CURLM_OK;
}
}
#endif
return CURLM_WAKEUP_FAILURE;
}
/*
@ -2309,6 +2412,11 @@ CURLMcode curl_multi_cleanup(struct Curl_multi *multi)
Curl_hash_destroy(&multi->hostcache);
Curl_psl_destroy(&multi->psl);
#ifdef ENABLE_WAKEUP
sclose(multi->wakeup_pair[0]);
sclose(multi->wakeup_pair[1]);
#endif
free(multi);
return CURLM_OK;