Messages in this thread | | | Date | Wed, 26 Aug 2009 16:10:52 +0200 | From | Heiko Carstens <> | Subject | Re: [PATCH 08/12] add trace events for each syscall entry/exit |
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On Wed, Aug 26, 2009 at 03:30:22PM +0200, Frederic Weisbecker wrote: > On Wed, Aug 26, 2009 at 02:59:43PM +0200, Heiko Carstens wrote: > > > Yeah, and as told before, syscalls tracing from kernel thread is > > > an interesting point but we can't do it that way. > > > > > > I'm queuing this patch for .32, but I need you Signed-off-by to apply it :) > > > > That won't always work as pointed out in the other example: > > - Process doing sys_init_module then scheduled away > > - User enables syscall tracing -> TIF_SYSCALL_FTRACE gets set > > - init function of the module gets called and is doing kernel_thread() > > (old API) -> kernel thread inherits TIF_SYSCALL_FTRACE. > > > > I don't think that's what you want. You might want to clear the flag for > > new processes during fork (only for kernel threads I would guess). > > > > At least the current patch leaves a hole. > > Ah, there are callsites that use kernel_thread() directly? > Does it means that t->mm could be non NULL for such resulting > kernel threads, in that case it would be hard to hook on > do_fork() to check that.
Oh yes, you are right. kernel threads created with kernel_thread() have t->mm != NULL if the forking process has an mm too.
There are very few callsites left which still use kernel_thread(). (the last one in s390 driver code will be gone after the next merge window).
As far as I can there are only four callsites left (excluding staging): jffs2 and three in net/bluetooth/*
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