On Fri, 8 Mar 2019 11:32:04 -0800 Douglas Anderson <diand...@chromium.org> wrote:
> As reported back in 2016-11 [1], the "ftdump" kdb command triggers a > BUG for "sleeping function called from invalid context". > > kdb's "ftdump" command wants to call ring_buffer_read_prepare() in > atomic context. A very simple solution for this is to add allocation > flags to ring_buffer_read_prepare() so kdb can call it without > triggering the allocation error. This patch does that. > > Note that in the original email thread about this, it was suggested > that perhaps the solution for kdb was to either preallocate the buffer > ahead of time or create our own iterator. I'm hoping that this > alternative of adding allocation flags to ring_buffer_read_prepare() > can be considered since it means I don't need to duplicate more of the > core trace code into "trace_kdb.c" (for either creating my own > iterator or re-preparing a ring allocator whose memory was already > allocated). > > NOTE: another option for kdb is to actually figure out how to make it > reuse the existing ftrace_dump() function and totally eliminate the > duplication. This sounds very appealing and actually works (the "sr > z" command can be seen to properly dump the ftrace buffer). The > downside here is that ftrace_dump() fully consumes the trace buffer. > Unless that is changed I'd rather not use it because it means "ftdump > | grep xyz" won't be very useful to search the ftrace buffer since it > will throw away the whole trace on the first grep. A future patch to > dump only the last few lines of the buffer will also be hard to > implement. > > [1] https://lkml.kernel.org/r/20161117191605.ga21...@google.com > > Reported-by: Brian Norris <briannor...@chromium.org> > Signed-off-by: Douglas Anderson <diand...@chromium.org> > --- > Thanks for sending this. I'm currently traveling and also have to get the merge window patches out, I wont be able to get to these till I have that settled. If you don't hear from me in a week, please send me a reminder. Thanks! -- Steve _______________________________________________ Kgdb-bugreport mailing list Kgdb-bugreport@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kgdb-bugreport
