[coreboot-gerrit] Change in coreboot[master]: arch/x86: Remove spinlock dependency on threading.

[Raul Rangel (Code Review)]

Raul Rangel has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/59322 )

Change subject: arch/x86: Remove spinlock dependency on threading.
......................................................................

arch/x86: Remove spinlock dependency on threading.

Since we only have one spinlock caller left, we can move the
thread_coop_ calls out of the spinlock.

This is mostly a revert of CB:56320.

BUG=b:179699789
TEST=Boot guybrush to OS with threading enabled

Signed-off-by: Raul E Rangel 
Change-Id: I55d0cd2bcd82721098ca24ae2368bb6a16a07df4
---
M src/arch/x86/include/arch/smp/spinlock.h
M src/console/printk.c
2 files changed, 9 insertions(+), 10 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/22/59322/1

diff --git a/src/arch/x86/include/arch/smp/spinlock.h b/src/arch/x86/include/arch/smp/spinlock.h
index c7008c1..f8fffdb 100644
--- a/src/arch/x86/include/arch/smp/spinlock.h
+++ b/src/arch/x86/include/arch/smp/spinlock.h
@@ -3,8 +3,6 @@
 #ifndef ARCH_SMP_SPINLOCK_H
 #define ARCH_SMP_SPINLOCK_H

-#include <thread.h>
-
 /*
  * Your basic SMP spinlocks, allowing only a single CPU anywhere
  */
@@ -52,16 +50,10 @@
    __asm__ __volatile__(
    	spin_lock_string
    	: "=m" (lock->lock) : : "memory");
-
-	/* Switching contexts while holding a spinlock will lead to deadlocks */
-	thread_coop_disable();
-
 }

static __always_inline void spin_unlock(spinlock_t *lock)
 {
-	thread_coop_enable();
-
    __asm__ __volatile__(
    	spin_unlock_string
    	: "=m" (lock->lock) : : "memory");
diff --git a/src/console/printk.c b/src/console/printk.c
index 1ed39cb..99e0151 100644
--- a/src/console/printk.c
+++ b/src/console/printk.c
@@ -8,11 +8,12 @@
 #include <console/console.h>
 #include <console/streams.h>
 #include <console/vtxprintf.h>
-#include <smp/spinlock.h>
 #include <smp/node.h>
+#include <smp/spinlock.h>
+#include <thread.h>
 #include <timer.h>

-DECLARE_SPIN_LOCK(console_lock)
+DECLARE_SPIN_LOCK(console_lock);

#define TRACK_CONSOLE_TIME (!ENV_SMM && CONFIG(HAVE_MONOTONIC_TIMER))

@@ -80,6 +81,10 @@
    if (log_this < CONSOLE_LOG_FAST)
    	return 0;

+	/* Context switching while holding a spin lock can lead to a dead lock. */
+	thread_coop_disable();
+
+	/* We use a spinlock instead of a mutex to allow coop-threading to use printk. */
    spin_lock(&console_lock);

console_time_run();
@@ -95,6 +100,8 @@

spin_unlock(&console_lock);

+	thread_coop_enable();
+
    return i;
 }