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nameserv: add asynchronous resolving with POSIX threads

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Run getaddrinfo()/gethostbyname() in separate thread to avoid blocking.
Only one resolving thread is running at one time, so this should work
also on systems where the functions are not thread-safe.
This commit is contained in:
Miroslav Lichvar
2014-04-23 17:50:36 +02:00
parent d243f1f8fe
commit 5483567190
3 changed files with 110 additions and 0 deletions
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95
nameserv_async.c
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@@ -30,10 +30,103 @@
#include "nameserv_async.h"
#include "logging.h"
#include "memory.h"
#include "sched.h"
#include "util.h"
#ifdef FEAT_ASYNCDNS
#ifdef USE_PTHREAD_ASYNCDNS
#include <pthread.h>
/* ================================================== */
struct DNS_Async_Instance {
const char *name;
DNS_Status status;
IPAddr addr;
DNS_NameResolveHandler handler;
void *arg;
pthread_t thread;
int pipe[2];
};
static int resolving_threads = 0;
/* ================================================== */
static void *
start_resolving(void *anything)
{
struct DNS_Async_Instance *inst = (struct DNS_Async_Instance *)anything;
inst->status = DNS_Name2IPAddress(inst->name, &inst->addr);
/* Notify the main thread that the result is ready */
if (write(inst->pipe[1], "", 1) < 0)
;
return NULL;
}
/* ================================================== */
static void
end_resolving(void *anything)
{
struct DNS_Async_Instance *inst = (struct DNS_Async_Instance *)anything;
if (pthread_join(inst->thread, NULL)) {
LOG_FATAL(LOGF_Nameserv, "pthread_join() failed");
}
resolving_threads--;
SCH_RemoveInputFileHandler(inst->pipe[0]);
close(inst->pipe[0]);
close(inst->pipe[1]);
(inst->handler)(inst->status, &inst->addr, inst->arg);
Free(inst);
}
/* ================================================== */
void
DNS_Name2IPAddressAsync(const char *name, DNS_NameResolveHandler handler, void *anything)
{
struct DNS_Async_Instance *inst;
inst = MallocNew(struct DNS_Async_Instance);
inst->name = name;
inst->handler = handler;
inst->arg = anything;
inst->status = DNS_Failure;
if (pipe(inst->pipe)) {
LOG_FATAL(LOGF_Nameserv, "pipe() failed");
}
resolving_threads++;
assert(resolving_threads <= 1);
if (pthread_create(&inst->thread, NULL, start_resolving, inst)) {
LOG_FATAL(LOGF_Nameserv, "pthread_create() failed");
}
SCH_AddInputFileHandler(inst->pipe[0], end_resolving, inst);
}
/* ================================================== */
#else
#error
#endif
#else
/* This is a blocking implementation used when nothing else is available */
void
@@ -47,3 +140,5 @@ DNS_Name2IPAddressAsync(const char *name, DNS_NameResolveHandler handler, void *
}
/* ================================================== */
#endif