* Russell King <rmk+kernel@xxxxxxxxxxxxxxx> [190125 21:04]: > Executing loops such as: > > while (1) > cpu_relax(); > > with interrupts disabled results in a livelock of the entire system, > as other CPUs are prevented making progress. This is most noticable > as a failure of crashdump kexec, which stops just after issuing: > > Loading crashdump kernel... > > to the system console. A workaround for this is to use 10 nops in > cpu_relax(). > > We also use wfe() in while (1) loops to avoid burning cycles in a > tight loop, giving the CPU a hint that we're not doing anything > useful. > > Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx> > --- > It's been a while since this was posted, Will's suggestion was to use > 10 nops in cpu_relax() last time around. I still prefer wfe() in > these infinite-not-doing-anything-ever loops. Works for me: Tested-by: Tony Lindgren <tony@xxxxxxxxxxx>
