[POWERPC] Fix might-sleep warning on removing cpus

Noticing the following might_sleep warning (dump_stack()) during kdump
testing when CONFIG_DEBUG_SPINLOCK_SLEEP is enabled. All secondary CPUs
will be calling rtas_set_indicator with interrupts disabled to remove
them from global interrupt queue.

BUG: sleeping function called from invalid context at
arch/powerpc/kernel/rtas.c:463
in_atomic():1, irqs_disabled():1
Call Trace:
[C00000000FFFB970] [C000000000010234] .show_stack+0x68/0x1b0 (unreliable)
[C00000000FFFBA10] [C000000000059354] .__might_sleep+0xd8/0xf4
[C00000000FFFBA90] [C00000000001D1BC] .rtas_busy_delay+0x20/0x5c
[C00000000FFFBB20] [C00000000001D8A8] .rtas_set_indicator+0x6c/0xcc
[C00000000FFFBBC0] [C000000000048BF4] .xics_teardown_cpu+0x118/0x134
[C00000000FFFBC40] [C00000000004539C]
.pseries_kexec_cpu_down_xics+0x74/0x8c
[C00000000FFFBCC0] [C00000000002DF08] .crash_ipi_callback+0x15c/0x188
[C00000000FFFBD50] [C0000000000296EC] .smp_message_recv+0x84/0xdc
[C00000000FFFBDC0] [C000000000048E08] .xics_ipi_dispatch+0xf0/0x130
[C00000000FFFBE50] [C00000000009EF10] .handle_IRQ_event+0x7c/0xf8
[C00000000FFFBF00] [C0000000000A0A14] .handle_percpu_irq+0x90/0x10c
[C00000000FFFBF90] [C00000000002659C] .call_handle_irq+0x1c/0x2c
[C00000000058B9C0] [C00000000000CA10] .do_IRQ+0xf4/0x1a4
[C00000000058BA50] [C0000000000044EC] hardware_interrupt_entry+0xc/0x10
 --- Exception: 501 at .plpar_hcall_norets+0x14/0x1c
   LR = .pseries_dedicated_idle_sleep+0x190/0x1d4
[C00000000058BD40] [C00000000058BDE0] 0xc00000000058bde0 (unreliable)
[C00000000058BDF0] [C00000000001270C] .cpu_idle+0x10c/0x1e0
[C00000000058BE70] [C000000000009274] .rest_init+0x44/0x5c

To fix this issue, rtas_set_indicator_fast() is added so that will not
wait for RTAS 'busy' delay and this new function is used for kdump (in
xics_teardown_cpu()) and for CPU hotplug ( xics_migrate_irqs_away() and
xics_setup_cpu()).

Note that the platform architecture spec says that set-indicator
on the indicator we're using here is not permitted to return the
busy or extended busy status codes.

Signed-off-by: Haren Myneni <haren@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 4a4cb5598402..77f1e06d208d 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -569,6 +569,27 @@ int rtas_set_indicator(int indicator, int index, int new_value)
 }
 EXPORT_SYMBOL(rtas_set_indicator);
 
+/*
+ * Ignoring RTAS extended delay
+ */
+int rtas_set_indicator_fast(int indicator, int index, int new_value)
+{
+        int rc;
+        int token = rtas_token("set-indicator");
+
+        if (token == RTAS_UNKNOWN_SERVICE)
+                return -ENOENT;
+
+        rc = rtas_call(token, 3, 1, NULL, indicator, index, new_value);
+
+        WARN_ON(rc == -2 || (rc >= 9900 && rc <= 9905));
+
+        if (rc < 0)
+                return rtas_error_rc(rc);
+
+        return rc;
+}
+
 void rtas_restart(char *cmd)
 {
         if (rtas_flash_term_hook)