diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2011-07-22 16:43:49 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-07-22 16:43:49 -0700 |
| commit | 391d6276db9fbdedfbc30e1b56390414f0e55988 (patch) | |
| tree | d22cd2482f5452d616ee981e954074ffc6ae094d /kernel/printk.c | |
| parent | 75b56ec294b074d70f8a676ab02611a3fea76cab (diff) | |
| parent | dd4e5d3ac4a76b868daf30e35bd572def96c30ed (diff) | |
Merge branch 'core-printk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-printk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
lockdep: Fix trace_[soft,hard]irqs_[on,off]() recursion
printk: Fix console_sem vs logbuf_lock unlock race
printk: Release console_sem after logbuf_lock
Diffstat (limited to 'kernel/printk.c')
| -rw-r--r-- | kernel/printk.c | 24 |
1 files changed, 21 insertions, 3 deletions
diff --git a/kernel/printk.c b/kernel/printk.c index 35185392173..37dff3429ad 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -782,7 +782,7 @@ static inline int can_use_console(unsigned int cpu) static int console_trylock_for_printk(unsigned int cpu) __releases(&logbuf_lock) { - int retval = 0; + int retval = 0, wake = 0; if (console_trylock()) { retval = 1; @@ -795,12 +795,14 @@ static int console_trylock_for_printk(unsigned int cpu) */ if (!can_use_console(cpu)) { console_locked = 0; - up(&console_sem); + wake = 1; retval = 0; } } printk_cpu = UINT_MAX; spin_unlock(&logbuf_lock); + if (wake) + up(&console_sem); return retval; } static const char recursion_bug_msg [] = @@ -1242,7 +1244,7 @@ void console_unlock(void) { unsigned long flags; unsigned _con_start, _log_end; - unsigned wake_klogd = 0; + unsigned wake_klogd = 0, retry = 0; if (console_suspended) { up(&console_sem); @@ -1251,6 +1253,7 @@ void console_unlock(void) console_may_schedule = 0; +again: for ( ; ; ) { spin_lock_irqsave(&logbuf_lock, flags); wake_klogd |= log_start - log_end; @@ -1271,8 +1274,23 @@ void console_unlock(void) if (unlikely(exclusive_console)) exclusive_console = NULL; + spin_unlock(&logbuf_lock); + up(&console_sem); + + /* + * Someone could have filled up the buffer again, so re-check if there's + * something to flush. In case we cannot trylock the console_sem again, + * there's a new owner and the console_unlock() from them will do the + * flush, no worries. + */ + spin_lock(&logbuf_lock); + if (con_start != log_end) + retry = 1; spin_unlock_irqrestore(&logbuf_lock, flags); + if (retry && console_trylock()) + goto again; + if (wake_klogd) wake_up_klogd(); } |