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authorNicholas Piggin <npiggin@gmail.com>2018-04-27 11:51:59 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2018-04-27 16:35:57 +1000
commit6029755eed95e5c90f763188c87ae3ff41e48e5c (patch)
tree912e2106089759f15a24f1e2f5bf384946c42878 /arch
parentc0f7f5b6c69107ca92909512533e70258ee19188 (diff)
powerpc: Fix deadlock with multiple calls to smp_send_stop
smp_send_stop can lock up the IPI path for any subsequent calls, because the receiving CPUs spin in their handler function. This started becoming a problem with the addition of an smp_send_stop call in the reboot path, because panics can reboot after doing their own smp_send_stop. The NMI IPI variant was fixed with ac61c11566 ("powerpc: Fix smp_send_stop NMI IPI handling"), which leaves the smp_call_function variant. This is fixed by having smp_send_stop only ever do the smp_call_function once. This is a bit less robust than the NMI IPI fix, because any other call to smp_call_function after smp_send_stop could deadlock, but that has always been the case, and it was not been a problem before. Fixes: f2748bdfe1573 ("powerpc/powernv: Always stop secondaries before reboot/shutdown") Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/kernel/smp.c55
1 files changed, 39 insertions, 16 deletions
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 3582f30b60b7..9ca7148b5881 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -565,17 +565,6 @@ void crash_send_ipi(void (*crash_ipi_callback)(struct pt_regs *))
}
#endif
-static void stop_this_cpu(void *dummy)
-{
- /* Remove this CPU */
- set_cpu_online(smp_processor_id(), false);
-
- hard_irq_disable();
- spin_begin();
- while (1)
- spin_cpu_relax();
-}
-
#ifdef CONFIG_NMI_IPI
static void nmi_stop_this_cpu(struct pt_regs *regs)
{
@@ -583,23 +572,57 @@ static void nmi_stop_this_cpu(struct pt_regs *regs)
* This is a special case because it never returns, so the NMI IPI
* handling would never mark it as done, which makes any later
* smp_send_nmi_ipi() call spin forever. Mark it done now.
+ *
+ * IRQs are already hard disabled by the smp_handle_nmi_ipi.
*/
nmi_ipi_lock();
nmi_ipi_busy_count--;
nmi_ipi_unlock();
- stop_this_cpu(NULL);
+ /* Remove this CPU */
+ set_cpu_online(smp_processor_id(), false);
+
+ spin_begin();
+ while (1)
+ spin_cpu_relax();
}
-#endif
void smp_send_stop(void)
{
-#ifdef CONFIG_NMI_IPI
smp_send_nmi_ipi(NMI_IPI_ALL_OTHERS, nmi_stop_this_cpu, 1000000);
-#else
+}
+
+#else /* CONFIG_NMI_IPI */
+
+static void stop_this_cpu(void *dummy)
+{
+ /* Remove this CPU */
+ set_cpu_online(smp_processor_id(), false);
+
+ hard_irq_disable();
+ spin_begin();
+ while (1)
+ spin_cpu_relax();
+}
+
+void smp_send_stop(void)
+{
+ static bool stopped = false;
+
+ /*
+ * Prevent waiting on csd lock from a previous smp_send_stop.
+ * This is racy, but in general callers try to do the right
+ * thing and only fire off one smp_send_stop (e.g., see
+ * kernel/panic.c)
+ */
+ if (stopped)
+ return;
+
+ stopped = true;
+
smp_call_function(stop_this_cpu, NULL, 0);
-#endif
}
+#endif /* CONFIG_NMI_IPI */
struct thread_info *current_set[NR_CPUS];