xnu-6153.141.1.tar.gz

[apple/xnu.git] / pexpert / i386 / pe_kprintf.c

diff --git a/pexpert/i386/pe_kprintf.c b/pexpert/i386/pe_kprintf.c
index 63e10d9f8e92d7671ce8a0e5a2facd7a65a48181..ce2ff230e865e80d1c9593efbabf52362faabed0 100644 (file)
--- a/pexpert/i386/pe_kprintf.c
+++ b/pexpert/i386/pe_kprintf.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2006 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 2000-2019 Apple Inc. All rights reserved.
  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  *
@@ -40,6 +40,12 @@
 #include <i386/proc_reg.h>
 #include <os/log_private.h>
 #include <libkern/section_keywords.h>
+#include <kern/processor.h>
+#include <kern/clock.h>
+#include <mach/clock_types.h>
+
+extern uint64_t LockTimeOut;
+extern processor_t      current_processor(void);
 
 /* Globals */
 void (*PE_kputc)(char c);
@@ -53,7 +59,7 @@ SECURITY_READ_ONLY_LATE(unsigned int) disable_serial_output = FALSE;
 SECURITY_READ_ONLY_LATE(unsigned int) disable_serial_output = TRUE;
 #endif
 
-decl_simple_lock_data(static, kprintf_lock)
+decl_simple_lock_data(static, kprintf_lock);
 
 void
 PE_init_kprintf(boolean_t vm_initialized)
@@ -110,6 +116,9 @@ _kprintf(const char *format, ...)
 
 static int cpu_last_locked = 0;
 
+#define KPRINTF_LOCKWAIT_PATIENT (LockTimeOut)
+#define KPRINTF_LOCKWAIT_IMPATIENT (LockTimeOut >> 4)
+
 __attribute__((noinline, not_tail_called))
 void
 kprintf(const char *fmt, ...)
@@ -117,6 +126,8 @@ kprintf(const char *fmt, ...)
        va_list    listp;
        va_list    listp2;
        boolean_t  state;
+       boolean_t  in_panic_context = FALSE;
+       unsigned int kprintf_lock_grabbed;
        void      *caller = __builtin_return_address(0);
 
        if (!disable_serial_output) {
@@ -142,17 +153,16 @@ kprintf(const char *fmt, ...)
                        return;
                }
 
-               /*
-                * Spin to get kprintf lock but poll for incoming signals
-                * while interrupts are masked.
-                */
                state = ml_set_interrupts_enabled(FALSE);
 
                pal_preemption_assert();
 
-               while (!simple_lock_try(&kprintf_lock, LCK_GRP_NULL)) {
-                       (void) cpu_signal_handler(NULL);
-               }
+               in_panic_context = processor_in_panic_context(current_processor());
+
+               // If current CPU is in panic context, be a little more impatient.
+               kprintf_lock_grabbed = simple_lock_try_lock_mp_signal_safe_loop_duration(&kprintf_lock,
+                   in_panic_context ? KPRINTF_LOCKWAIT_IMPATIENT : KPRINTF_LOCKWAIT_PATIENT,
+                   LCK_GRP_NULL);
 
                if (cpu_number() != cpu_last_locked) {
                        MP_DEBUG_KPRINTF("[cpu%d...]\n", cpu_number());
@@ -164,7 +174,10 @@ kprintf(const char *fmt, ...)
                _doprnt(fmt, &listp, PE_kputc, 16);
                va_end(listp);
 
-               simple_unlock(&kprintf_lock);
+               if (kprintf_lock_grabbed) {
+                       simple_unlock(&kprintf_lock);
+               }
+
                ml_set_interrupts_enabled(state);
 
                // If interrupts are enabled