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authorNicholas Piggin <npiggin@gmail.com>2016-12-20 04:30:11 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2017-04-28 21:26:46 +1000
commit1cd6ed7c2e35a716dcf1347c33f58a7ce7d1414f (patch)
tree3f0c0db79e2c10d034bc3b52ad1c5307ecc27cd3 /arch/powerpc/xmon
parent102c05e8dc4f75a573437e2ce50b2559f3db8d5e (diff)
powerpc/xmon: Wait for secondaries before IPI'ing on system reset
An externally triggered system reset (e.g., via QEMU nmi command, or pseries reset button) can cause system reset interrupts on all CPUs. In case this causes xmon to be entered, it is undesirable for the primary (first) CPU into xmon to trigger an NMI IPI to others, because this may cause a nested system reset interrupt. So spin for a time waiting for secondaries to join xmon before performing the NMI IPI, similarly to what the crash dump code does. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> [mpe: Only do it when we come in from system reset, not via sysrq etc.] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/xmon')
-rw-r--r--arch/powerpc/xmon/xmon.c36
1 files changed, 27 insertions, 9 deletions
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 682506821bba..da5619847517 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -418,7 +418,22 @@ int cpus_are_in_xmon(void)
{
return !cpumask_empty(&cpus_in_xmon);
}
-#endif
+
+static bool wait_for_other_cpus(int ncpus)
+{
+ unsigned long timeout;
+
+ /* We wait for 2s, which is a metric "little while" */
+ for (timeout = 20000; timeout != 0; --timeout) {
+ if (cpumask_weight(&cpus_in_xmon) >= ncpus)
+ return true;
+ udelay(100);
+ barrier();
+ }
+
+ return false;
+}
+#endif /* CONFIG_SMP */
static inline int unrecoverable_excp(struct pt_regs *regs)
{
@@ -440,7 +455,6 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
#ifdef CONFIG_SMP
int cpu;
int secondary;
- unsigned long timeout;
#endif
local_irq_save(flags);
@@ -527,13 +541,17 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
xmon_owner = cpu;
mb();
if (ncpus > 1) {
- smp_send_debugger_break();
- /* wait for other cpus to come in */
- for (timeout = 100000000; timeout != 0; --timeout) {
- if (cpumask_weight(&cpus_in_xmon) >= ncpus)
- break;
- barrier();
- }
+ /*
+ * A system reset (trap == 0x100) can be triggered on
+ * all CPUs, so when we come in via 0x100 try waiting
+ * for the other CPUs to come in before we send the
+ * debugger break (IPI). This is similar to
+ * crash_kexec_secondary().
+ */
+ if (TRAP(regs) != 0x100 || !wait_for_other_cpus(ncpus))
+ smp_send_debugger_break();
+
+ wait_for_other_cpus(ncpus);
}
remove_bpts();
disable_surveillance();