I have a driver that needs to be SMP-safe. It also has some code hooking
into the net_rx_action softirq. So it takes a spinlock and disables the
local bottom-half around its critical sections:
spin_lock_bh(&driver_lock). Now, I'm facing a deadlock under a
particular sequence involving the files_lock:
1. CPU 0 takes driver_lock and then calls remove_proc_entry() which is
hanging at spin_lock(&files_lock).
2. CPU 1 was in fput() which took files_lock; the softirq comes in at
this point and attempts to take driver_lock and hangs forever.
It seems this kind of a deadlock can happen with any kernel lock, not
just files_lock. What's the driver's mistake here? Is it wrong to call
remove_proc_entry() while holding another lock? What is the right thing
to do?
This is with the 2.4 kernel, BTW.
thanks
srini
On Thu, Dec 20, 2007 at 10:59:20PM -0800, Srinivas Kommu wrote:
> It seems this kind of a deadlock can happen with any kernel lock, not
> just files_lock. What's the driver's mistake here? Is it wrong to call
> remove_proc_entry() while holding another lock? What is the right thing
> to do?
remove_proc_entry() is a blocking function...