From 0e56d9738da8bb81d31616f75c8201f373d7b618 Mon Sep 17 00:00:00 2001
From: "Dmitry E. Oboukhov" <unera@debian.org>
Date: Fri, 14 Dec 2012 02:32:54 +0400
Subject: [PATCH] try to fix race condition
---
src/ipc.m | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/src/ipc.m b/src/ipc.m
index 27d507c5da..889f57926e 100644
--- a/src/ipc.m
+++ b/src/ipc.m
@@ -35,6 +35,8 @@ const ev_tstamp IPC_TIMEOUT_INFINITY = 365*86400*100.0;
struct ipc_channel {
struct rlist readers, writers;
+ unsigned creaders;
+ unsigned cwriters;
unsigned size;
unsigned beg;
unsigned count;
@@ -73,6 +75,8 @@ void
ipc_channel_init(struct ipc_channel *ch)
{
ch->beg = ch->count = 0;
+ ch->creaders = 0;
+ ch->cwriters = 0;
rlist_init(&ch->readers);
rlist_init(&ch->writers);
}
@@ -96,12 +100,13 @@ void *
ipc_channel_get_timeout(struct ipc_channel *ch, ev_tstamp timeout)
{
/* channel is empty */
- if (!ch->count) {
+ if (ch->count == 0 || ch->creaders >= ch->count) {
rlist_add_tail_entry(&ch->readers, fiber, state);
+ ch->creaders++;
bool cancellable = fiber_setcancellable(true);
-
bool timed_out = fiber_yield_timeout(timeout);
rlist_del_entry(fiber, state);
+ ch->creaders--;
fiber_testcancel();
fiber_setcancellable(cancellable);
@@ -115,6 +120,7 @@ ipc_channel_get_timeout(struct ipc_channel *ch, ev_tstamp timeout)
}
}
+ assert(ch->count > 0);
void *res = ch->item[ch->beg];
if (++ch->beg >= ch->size)
ch->beg -= ch->size;
@@ -127,6 +133,7 @@ ipc_channel_get_timeout(struct ipc_channel *ch, ev_tstamp timeout)
fiber_wakeup(f);
}
+
return res;
}
@@ -141,13 +148,15 @@ ipc_channel_put_timeout(struct ipc_channel *ch, void *data,
ev_tstamp timeout)
{
/* channel is full */
- if (ch->count >= ch->size) {
+ if (ch->count >= ch->size || ch->cwriters >= ch->size - ch->count) {
rlist_add_tail_entry(&ch->writers, fiber, state);
+ ch->cwriters++;
bool cancellable = fiber_setcancellable(true);
bool timed_out = fiber_yield_timeout(timeout);
rlist_del_entry(fiber, state);
+ ch->cwriters--;
fiber_testcancel();
fiber_setcancellable(cancellable);
@@ -156,9 +165,10 @@ ipc_channel_put_timeout(struct ipc_channel *ch, void *data,
errno = ETIMEDOUT;
return -1;
}
-
}
+ assert(ch->count < ch->size);
+
unsigned i = ch->beg;
i += ch->count;
ch->count++;
--
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