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authorNicholas Piggin <npiggin@gmail.com>2018-04-25 05:17:53 +0300
committerMichael Ellerman <mpe@ellerman.id.au>2018-04-25 13:38:08 +0300
commitac61c1156623455c46701654abd8c99720bceea1 (patch)
treec7f94e67f672b815fc5815d3f4ce7af623359f3e /arch
parent682e6b4da5cbe8e9a53f979a58c2a9d7dc997175 (diff)
downloadlinux-ac61c1156623455c46701654abd8c99720bceea1.tar.xz
powerpc: Fix smp_send_stop NMI IPI handling
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: 6bed3237624e3 ("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>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/kernel/smp.c22
1 files changed, 17 insertions, 5 deletions
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index e16ec7b3b427..3582f30b60b7 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -565,11 +565,7 @@ void crash_send_ipi(void (*crash_ipi_callback)(struct pt_regs *))
}
#endif
-#ifdef CONFIG_NMI_IPI
-static void stop_this_cpu(struct pt_regs *regs)
-#else
static void stop_this_cpu(void *dummy)
-#endif
{
/* Remove this CPU */
set_cpu_online(smp_processor_id(), false);
@@ -580,10 +576,26 @@ static void stop_this_cpu(void *dummy)
spin_cpu_relax();
}
+#ifdef CONFIG_NMI_IPI
+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.
+ */
+ nmi_ipi_lock();
+ nmi_ipi_busy_count--;
+ nmi_ipi_unlock();
+
+ stop_this_cpu(NULL);
+}
+#endif
+
void smp_send_stop(void)
{
#ifdef CONFIG_NMI_IPI
- smp_send_nmi_ipi(NMI_IPI_ALL_OTHERS, stop_this_cpu, 1000000);
+ smp_send_nmi_ipi(NMI_IPI_ALL_OTHERS, nmi_stop_this_cpu, 1000000);
#else
smp_call_function(stop_this_cpu, NULL, 0);
#endif