Re: [Dazuko-devel] dazukofs-3.0.0 interrupted system calls

[John Ogness]

[ Sorry. I accidentally sent the last message while still writing
  it. Here is my complete response. ]

On 2009-02-26, Frantisek Hrbata <address@hidden> wrote:
> I experimentally added support for dazukofs to our upcoming avg8
> because I would like to make some performance comparison between
> dazukofs and avflt.

Nice. It would be great if you could post the results of your tests
here.

> After dazukofs integration to our scanner I have noticed that
> dazukofs_get_access returns a lots of -EINTR. I am using dazukofs in
> a multi-threaded scanner and this error occurs only when more then
> one thread is used. I wrote a simple showfiles_mt application using
> dazukofs in several threads just to check out if the problem is in
> my integration or in dazukofs. As I found out I can easily reproduce
> this behavior with showfiles_mt.

I am running a multi-threaded application without any such
problems. However, my implementation is slightly different then
yours. I will illustrate the difference here using a diff-like
approach.

int main(void)
{
     ...
-    signal(SIGTERM, sigterm);
-    signal(SIGINT, sigterm);
+    sigset_t sigset;
+
+    /* catch TERM,INT,HUP signals */
+    signal(SIGTERM, sigterm);
+    signal(SIGINT, sigterm);
+    signal(SIGHUP, sigterm);
+
+    /* ignore SIGUSR1 (only used by threads) */
+    if (sigemptyset(&sigset) == 0) {
+       sigaddset(&sigset, SIGUSR1);
+       sigprocmask(SIG_BLOCK, &sigset, NULL);
+    }

So far the only difference is catching the HUP signal and explicitly
ignoring USR1. (HUP is the signal X sends if the X environment is
closed.)

void *thread_proc(void *data)
{
     ...
-    sigemptyset(&sigset);
-    sigaddset(&sigset, SIGINT);
-    sigaddset(&sigset, SIGTERM);
-    pthread_sigmask(SIG_BLOCK, &sigset, NULL);
-    sigaddset(&sigset, SIGUSR1);
-    pthread_sigmask(SIG_UNBLOCK, &sigset, NULL);
+    /* ignore TERM,INT,HUP signals within threads */
+    if (sigemptyset(&sigset) == 0) {
+       sigaddset(&sigset, SIGTERM);
+       sigaddset(&sigset, SIGINT);
+       sigaddset(&sigset, SIGHUP);
+       pthread_sigmask(SIG_BLOCK, &sigset, NULL);
+    }
+
+    /* catch USR1 signal within threads */
+    if (sigemptyset(&sigset) == 0) {
+       sigaddset(&sigset, SIGUSR1);
+       pthread_sigmask(SIG_UNBLOCK, &sigset, NULL);
+    }

Again there is the difference with the HUP signal. But I also notice
that you don't clear the set before setting up the unblock. So you are
effectively unblocking everything you had already set to
block. I suspect that is your problem.

> Also there is just a simple single process example shipped within
> dazukofs package so I am not sure if I am using it right.

I will add a multi-threaded showfiles to the next release package.

John Ogness

-- 
Dazuko Maintainer