Re: mimeheaders etc

[Matti Aarnio <mea@nic.funet.fi>]

On Fri, Dec 01, 2000 at 01:00:17PM +0300, Eugene Crosser wrote:
> >    Could you  truss  such process to see if it does some syscalls ?
> >    (It would, after all, spend a lot more CPU if it were busy spinning..)
> 
> Possibly this is some Solaris speciality:
> 
> ...
> link("/var/virtual/online.ru/mail/F/F/owen2000.L2a3c.3a27745d.80c4e5bf",
> "/var/virtual/online.ru/mail/F/F/owen2000.lock") = 0
> stat("/var/virtual/online.ru/mail/F/F/owen2000.L2a3c.3a27745d.80c4e5bf",
> 0xFFBEE0E8) = 0
> unlink("/var/virtual/online.ru/mail/F/F/owen2000.L2a3c.3a27745d.80c4e5bf") = 0

	This is mailbox dot-lock.

> lseek(7, 0, SEEK_SET)                           = 0
> fcntl(7, F_SETLKW, 0xFFBEEA5C)  (sleeping...)

	And this is FCNTL-lock of the same.
	... and THAT one is SLEEPing.  Why ?  Who else blocks it ?
	(User reading the mailbox ?)

	Some other process holds the lock, obviously.
	(I sure hope it doesn't do FCNTL+DOTLOCK in that order,
	 if it does, we have deadlock danger..)

> signotifywait()                 (sleeping...)
> door_return(0x00000000, 0, 0x00000000, 0) (sleeping...)
> lwp_cond_wait(0xFF0BF618, 0xFF0BF628, 0xFF073CA0) (sleeping...)
> lwp_sema_wait(0xFF0BC8D8)       (sleeping...)
>
> and here it stops scrolling and waits.  Does not make very much sense to
> me, though...

	The door_*() stuff on Solaris is used for resolver, and syslog,
	I recall.  It is some sort of RPC call mechanism sharing some
	of caller's process context while executing the remote side.

	Solaris 7 adds those lwp things to everything, including non-
	threaded software, and I think that is simply sleep().
	(Or then it is part of the door_call() )

> ...  Other case, same process:
> 
> write(1, " # h u n g r y\n", 8)                 = 8
> read(0, " # i d l e\n", 8192)                   = 6
> write(1, " # h u n g r y\n", 8)                 = 8
> read(0, 0x0005395C, 8192)       (sleeping...)
> signotifywait()                 (sleeping...)
> door_return(0x00000000, 0, 0x00000000, 0) (sleeping...)
> lwp_cond_wait(0xFF0BF618, 0xFF0BF628, 0xFF073CA0) (sleeping...)
> lwp_sema_wait(0xFF0BC8D8)       (sleeping...)


	Perhaps it is that thread stuff -- the CLUE here is that
	read() is SLEEPING.  All the rest is propably LWP switching.
	( ... non linearly thinking, now I spotted that above the
	  FCNTL is also sleeping... )

	Perhaps the '-l' option of 'truss' clues more by listing also
	the LWP id on each line.  (At least per Solaris 2.6 documentation.)

> Eugene

-- 
/Matti Aarnio	<mea@nic.funet.fi>