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authorJan Kara <jack@suse.cz>2014-06-04 16:11:36 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-04 16:54:16 -0700
commitbd8d7cf5b8410fe98eba06a9aaa90efe88815d8a (patch)
treec00e0af9d7fbed0b5e6d89d7b2b8348513103328 /kernel/printk
parent608873cacb9d0d2811586fcc79a38b64eabd6d32 (diff)
printk: fix lockdep instrumentation of console_sem
Printk calls mutex_acquire() / mutex_release() by hand to instrument lockdep about console_sem. However in some corner cases the instrumentation is missing. Fix the problem by creating helper functions for locking / unlocking console_sem which take care of lockdep instrumentation as well. Signed-off-by: Jan Kara <jack@suse.cz> Reported-by: Fabio Estevam <festevam@gmail.com> Reported-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Tested-by: Fabio Estevam <fabio.estevam@freescale.com> Tested-By: Valdis Kletnieks <valdis.kletnieks@vt.edu> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/printk')
-rw-r--r--kernel/printk/printk.c46
1 files changed, 32 insertions, 14 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 6e1b21a8a497..5ba37f813723 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -91,6 +91,29 @@ static struct lockdep_map console_lock_dep_map = {
#endif
/*
+ * Helper macros to handle lockdep when locking/unlocking console_sem. We use
+ * macros instead of functions so that _RET_IP_ contains useful information.
+ */
+#define down_console_sem() do { \
+ down(&console_sem);\
+ mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
+} while (0)
+
+static int __down_trylock_console_sem(unsigned long ip)
+{
+ if (down_trylock(&console_sem))
+ return 1;
+ mutex_acquire(&console_lock_dep_map, 0, 1, ip);
+ return 0;
+}
+#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
+
+#define up_console_sem() do { \
+ mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
+ up(&console_sem);\
+} while (0)
+
+/*
* This is used for debugging the mess that is the VT code by
* keeping track if we have the console semaphore held. It's
* definitely not the perfect debug tool (we don't know if _WE_
@@ -1422,7 +1445,7 @@ static int console_trylock_for_printk(unsigned int cpu)
*/
if (!can_use_console(cpu)) {
console_locked = 0;
- up(&console_sem);
+ up_console_sem();
return 0;
}
return 1;
@@ -1951,16 +1974,14 @@ void suspend_console(void)
printk("Suspending console(s) (use no_console_suspend to debug)\n");
console_lock();
console_suspended = 1;
- up(&console_sem);
- mutex_release(&console_lock_dep_map, 1, _RET_IP_);
+ up_console_sem();
}
void resume_console(void)
{
if (!console_suspend_enabled)
return;
- down(&console_sem);
- mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
+ down_console_sem();
console_suspended = 0;
console_unlock();
}
@@ -2002,12 +2023,11 @@ void console_lock(void)
{
might_sleep();
- down(&console_sem);
+ down_console_sem();
if (console_suspended)
return;
console_locked = 1;
console_may_schedule = 1;
- mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
}
EXPORT_SYMBOL(console_lock);
@@ -2021,15 +2041,14 @@ EXPORT_SYMBOL(console_lock);
*/
int console_trylock(void)
{
- if (down_trylock(&console_sem))
+ if (down_trylock_console_sem())
return 0;
if (console_suspended) {
- up(&console_sem);
+ up_console_sem();
return 0;
}
console_locked = 1;
console_may_schedule = 0;
- mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_);
return 1;
}
EXPORT_SYMBOL(console_trylock);
@@ -2091,7 +2110,7 @@ void console_unlock(void)
bool retry;
if (console_suspended) {
- up(&console_sem);
+ up_console_sem();
return;
}
@@ -2153,7 +2172,6 @@ skip:
local_irq_restore(flags);
}
console_locked = 0;
- mutex_release(&console_lock_dep_map, 1, _RET_IP_);
/* Release the exclusive_console once it is used */
if (unlikely(exclusive_console))
@@ -2161,7 +2179,7 @@ skip:
raw_spin_unlock(&logbuf_lock);
- up(&console_sem);
+ up_console_sem();
/*
* Someone could have filled up the buffer again, so re-check if there's
@@ -2206,7 +2224,7 @@ void console_unblank(void)
* oops_in_progress is set to 1..
*/
if (oops_in_progress) {
- if (down_trylock(&console_sem) != 0)
+ if (down_trylock_console_sem() != 0)
return;
} else
console_lock();