PMP hot plug issue in kernel

[Bhartiya Anju-B07263]

Hi All,
 
Recently came across an issue which is decribed below.
 
Setup: Port Multiplier with 2 HDD's connected to it; Port multiplier is
connected to a SATA port of the Host Controller.
 
Test: HDD1 is mounted and using dd command a file of size 512MB is being
written on it.
Command: time sh -c "dd if=/dev/zero of=/mnt/hd/ddfile bs=1k
count=512000 && sync"
 
While this command is running, if the second HDD on PMP is plugged out,
the R/W speed of the first HDD gets affected.
Please see the results of experiments on 2.6.31 kernel.
 
Plug Out	 Plug in	 Normal	
real    0m34.433s
user    0m0.932s
sys     0m21.352s	 real    0m23.726s
user    0m0.908s
sys     0m21.388s	 real    0m23.329s
user    0m1.132s
sys     0m20.968s	
 
The results are similiar with multiple Port Multipliers (Si3726, Si4726
and EXAR PMP) and multiple Host controllers (Si3132  and sata_fsl).
 
As the behaviour with multiple Host controllers and Port Multipliers is
the same so this seems to be an issue with libata stack.
Is there already a patch for this issue? Any pointers or help to fix
this will be greatly appreciated.
 
Best Regards,
Anju
Applications Engineer 
Freescale Semiconductor
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