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authorBenjamin Herrenschmidt <benh@kernel.crashing.org>2009-06-16 16:42:49 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2009-06-26 14:37:27 +1000
commitf97bb36f705da0a86b3ea77bfeee3415fee0b025 (patch)
tree753cfb89d52d5732142bb424b5c72ffc869db0a8
parent5d38902c483881645ba16058cffaa478b81e5cfa (diff)
powerpc/rtas: Turn rtas lock into a raw spinlock
RTAS currently uses a normal spinlock. However it can be called from contexts where this is not necessarily a good idea. For example, it can be called while syncing timebases, with the core timebase being frozen. Unfortunately, that will deadlock in case of lock contention when spinlock debugging is enabled as the spin lock debugging code will try to use __delay() which ... relies on the timebase being enabled. Also RTAS can be used in some low level IRQ handling code path so it may as well be a raw spinlock for -rt sake. Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
-rw-r--r--arch/powerpc/include/asm/rtas.h2
-rw-r--r--arch/powerpc/kernel/rtas.c38
2 files changed, 30 insertions, 10 deletions
diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
index 01c12339b304..0af42d20b692 100644
--- a/arch/powerpc/include/asm/rtas.h
+++ b/arch/powerpc/include/asm/rtas.h
@@ -58,7 +58,7 @@ struct rtas_t {
unsigned long entry; /* physical address pointer */
unsigned long base; /* physical address pointer */
unsigned long size;
- spinlock_t lock;
+ raw_spinlock_t lock;
struct rtas_args args;
struct device_node *dev; /* virtual address pointer */
};
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index ee4c7609b649..d9a9974c6938 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -40,7 +40,7 @@
#include <asm/atomic.h>
struct rtas_t rtas = {
- .lock = SPIN_LOCK_UNLOCKED
+ .lock = __RAW_SPIN_LOCK_UNLOCKED
};
EXPORT_SYMBOL(rtas);
@@ -67,6 +67,28 @@ unsigned long rtas_rmo_buf;
void (*rtas_flash_term_hook)(int);
EXPORT_SYMBOL(rtas_flash_term_hook);
+/* RTAS use home made raw locking instead of spin_lock_irqsave
+ * because those can be called from within really nasty contexts
+ * such as having the timebase stopped which would lockup with
+ * normal locks and spinlock debugging enabled
+ */
+static unsigned long lock_rtas(void)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ preempt_disable();
+ __raw_spin_lock_flags(&rtas.lock, flags);
+ return flags;
+}
+
+static void unlock_rtas(unsigned long flags)
+{
+ __raw_spin_unlock(&rtas.lock);
+ local_irq_restore(flags);
+ preempt_enable();
+}
+
/*
* call_rtas_display_status and call_rtas_display_status_delay
* are designed only for very early low-level debugging, which
@@ -79,7 +101,7 @@ static void call_rtas_display_status(char c)
if (!rtas.base)
return;
- spin_lock_irqsave(&rtas.lock, s);
+ s = lock_rtas();
args->token = 10;
args->nargs = 1;
@@ -89,7 +111,7 @@ static void call_rtas_display_status(char c)
enter_rtas(__pa(args));
- spin_unlock_irqrestore(&rtas.lock, s);
+ unlock_rtas(s);
}
static void call_rtas_display_status_delay(char c)
@@ -411,8 +433,7 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...)
if (!rtas.entry || token == RTAS_UNKNOWN_SERVICE)
return -1;
- /* Gotta do something different here, use global lock for now... */
- spin_lock_irqsave(&rtas.lock, s);
+ s = lock_rtas();
rtas_args = &rtas.args;
rtas_args->token = token;
@@ -439,8 +460,7 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...)
outputs[i] = rtas_args->rets[i+1];
ret = (nret > 0)? rtas_args->rets[0]: 0;
- /* Gotta do something different here, use global lock for now... */
- spin_unlock_irqrestore(&rtas.lock, s);
+ unlock_rtas(s);
if (buff_copy) {
log_error(buff_copy, ERR_TYPE_RTAS_LOG, 0);
@@ -837,7 +857,7 @@ asmlinkage int ppc_rtas(struct rtas_args __user *uargs)
buff_copy = get_errorlog_buffer();
- spin_lock_irqsave(&rtas.lock, flags);
+ flags = lock_rtas();
rtas.args = args;
enter_rtas(__pa(&rtas.args));
@@ -848,7 +868,7 @@ asmlinkage int ppc_rtas(struct rtas_args __user *uargs)
if (args.rets[0] == -1)
errbuf = __fetch_rtas_last_error(buff_copy);
- spin_unlock_irqrestore(&rtas.lock, flags);
+ unlock_rtas(flags);
if (buff_copy) {
if (errbuf)