Merge tag 'for-5.17/parisc-1' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux

Pull parisc architecture updates from Helge Deller:

 - Fix lpa and lpa_user defines (John David Anglin)

 - Fix symbol lookup of init functions with an __is_kernel() fix (Helge
   Deller)

 - Fix wrong pdc_toc_pim_11 and pdc_toc_pim_20 definitions (Helge
   Deller)

 - Add lws_atomic_xchg and lws_atomic_store syscalls (John David Anglin)

 - Rewrite light-weight syscall and futex code (John David Anglin)

 - Enable TOC (transfer of contents) feature unconditionally (Helge
   Deller)

 - Improve fault handler messages (John David Anglin)

 - Improve build process (Masahiro Yamada)

 - Reduce kernel code footprint of user access functions (Helge Deller)

 - Fix build error due to outX() macros (Bart Van Assche)

 - Ue default_groups in kobj_type in pdc_stable (Greg Kroah-Hartman)

 - Default to 16 CPUs on 32-bit kernel (Helge Deller)

* tag 'for-5.17/parisc-1' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  parisc: Default to 16 CPUs on 32-bit kernel
  sections: Fix __is_kernel() to include init ranges
  parisc: Re-use toc_stack as hpmc_stack
  parisc: Enable TOC (transfer of contents) feature unconditionally
  parisc: io: Improve the outb(), outw() and outl() macros
  parisc: pdc_stable: use default_groups in kobj_type
  parisc: Add kgdb io_module to read chars via PDC
  parisc: Fix pdc_toc_pim_11 and pdc_toc_pim_20 definitions
  parisc: Add lws_atomic_xchg and lws_atomic_store syscalls
  parisc: Rewrite light-weight syscall and futex code
  parisc: Enhance page fault termination message
  parisc: Don't call faulthandler_disabled() in do_page_fault()
  parisc: Switch user access functions to signal errors in r29 instead of r8
  parisc: Avoid calling faulthandler_disabled() twice
  parisc: Fix lpa and lpa_user defines
  parisc: Define depi_safe macro
  parisc: decompressor: do not copy source files while building

1 files changed, 16 insertions, 2 deletions

diff --git a/arch/parisc/kernel/toc.c b/arch/parisc/kernel/toc.c
index 18327611cf8f..be9a0bebe61e 100644
--- a/arch/parisc/kernel/toc.c
+++ b/arch/parisc/kernel/toc.c
@@ -9,8 +9,10 @@
 
 #include <asm/pdc.h>
 #include <asm/pdc_chassis.h>
+#include <asm/ldcw.h>
 
-unsigned int __aligned(16) toc_lock = 1;
+static unsigned int __aligned(16) toc_lock = 1;
+DEFINE_PER_CPU_PAGE_ALIGNED(char [16384], toc_stack);
 
 static void toc20_to_pt_regs(struct pt_regs *regs, struct pdc_toc_pim_20 *toc)
 {
@@ -63,7 +65,8 @@ void notrace __noreturn __cold toc_intr(struct pt_regs *regs)
 	struct pdc_toc_pim_20 pim_data20;
 	struct pdc_toc_pim_11 pim_data11;
 
-	nmi_enter();
+	/* verify we wrote regs to the correct stack */
+	BUG_ON(regs != (struct pt_regs *)&per_cpu(toc_stack, raw_smp_processor_id()));
 
 	if (boot_cpu_data.cpu_type >= pcxu) {
 		if (pdc_pim_toc20(&pim_data20))
@@ -76,14 +79,25 @@ void notrace __noreturn __cold toc_intr(struct pt_regs *regs)
 	}
 
 #ifdef CONFIG_KGDB
+	nmi_enter();
+
 	if (atomic_read(&kgdb_active) != -1)
 		kgdb_nmicallback(raw_smp_processor_id(), regs);
 	kgdb_handle_exception(9, SIGTRAP, 0, regs);
 #endif
+
+	/* serialize output, otherwise all CPUs write backtrace at once */
+	while (__ldcw(&toc_lock) == 0)
+		; /* wait */
 	show_regs(regs);
+	toc_lock = 1;	 /* release lock for next CPU */
+
+	if (raw_smp_processor_id() != 0)
+		while (1) ; /* all but monarch CPU will wait endless. */
 
 	/* give other CPUs time to show their backtrace */
 	mdelay(2000);
+
 	machine_restart("TOC");
 
 	/* should never reach this */