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Nicholas Piggin authored
The NMI IPI handler for a receiving CPU increments nmi_ipi_busy_count over the handler function call, which causes later smp_send_nmi_ipi() callers to spin until the call is finished. The stop_this_cpu() function never returns, so the busy count is never decremeted, which can cause the system to hang in some cases. For example panic() will call smp_send_stop() early on which calls stop_this_cpu() on other CPUs, then later in the reboot path, pnv_restart() will call smp_send_stop() again, which hangs. Fix this by adding a special case to the stop_this_cpu() handler to decrement the busy count, because it will never return. Now that the NMI/non-NMI versions of stop_this_cpu() are different, split them out into separate functions rather than doing #ifdef tricks to share the body between the two functions. Fixes: 6bed3237 ("powerpc: use NMI IPI for smp_send_stop") Reported-by:
Abdul Haleem <abdhalee@linux.vnet.ibm.com> Signed-off-by:
Nicholas Piggin <npiggin@gmail.com> [mpe: Split out the functions, tweak change log a bit] Signed-off-by:
Michael Ellerman <mpe@ellerman.id.au>
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