Re: [PATCH[ udevd race conditions and performance, assorted cleanups

[Kay Sievers <kay.sievers@vrfy.org>]

On Fri, Mar 26, 2004 at 11:48:15PM -0500, Chris Friesen wrote:
> 
> This patch covers a number of areas:
> 
> 1) sysfs.h is fixed up to use the common dbg() macro.  This fixes the 
> case where DEBUG is defined but USE_LOG isn't.
> 
> 2) udevstart.c is modified to include the proper headers, rather than 
> getting them indirectly which can break depending on Makefile flags
> 
> 3) udevd.c gets some major changes:
> a) I added a pipe from the signal handler.  This fixes the race 
> conditions that I mentioned earlier.  Basically, the point of the pipe 
> is to force the select() call to return immediately if a signal handler 
> fired before we actually started the select() call.  This then lets us 
> run the appropriate code based on flags set in the signal handler proper.
> b) I added a number of flags to coalesce calls to common routines.  This 
> should make things slightly more efficient.
> c) since most calls will tend to come in with a sequence number larger 
> than what has been received, I switched msg_queue_insert() to scan the 
> msg_list backwards to improve performance.

Looks really nice, seems a bit faster too.
Whitespace is broken, no tabs?


>  	while (1) {
> -		handle_msg(ssock);
> -
> -		while(msg_q_timeout) {
> -			msg_q_timeout = 0;
> -			msg_queue_manager();
> +		fd_set workreadfds = readfds;
> +		retval = select(maxsockplus, &workreadfds, NULL, NULL, NULL);
> +		
> +		if (retval < 0) {
> +			dbg("error in select: %s", strerror(errno));
> +			continue;

We interrupt select() intentionally, so better do not call it
"error" in syslog :)

thanks,
Kay


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