linux-kernel - FW: System Hang while trying to send over TCP socket with very less free m/m

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Message-ID: <BLU141-W7E99313C2CA3BE069EC5DD4120@phx.gbl>
Date:	Wed, 29 Jul 2009 13:54:27 +0530
From:	manu gautam <manugautam25@...mail.com>
To:	<netdev@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: FW: System Hang while trying to send over TCP socket with very less
 free m/m

Hi,

I am running 2.6.12 kernel with kernel PREEMPTION being OFF. 
While sending data over TCP socket I am experiencing system hang. What is happening actually is that the system is low in free memory and the sk_stream_alloc_pskb call in tcp_sendmsg fails and the control goes to "sk_stream_wait_memory" function. Inside this function we are calling schedule_timeout only if "sk_stream_memory_free(sk) && vm_wait" check is false. In my case what happens is that this check is always true and we don't do schedule_timeout which results in the system hang.
With preemption being OFF it becomes a kind of deadlock where the one thread is waiting for the memory to be freed but it is not getting scheduled out. 

I also checked on the latest kernel but there also I dont see any fix for this issue. 

Please excuse me if I have pasted it to some wrong mailing list.
Regards,Manu
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