linux-kernel - [PATCH v1 4/5] intel_th: msu: Prevent freeing buffers while locked windows exist

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Message-Id: <20190705141425.19894-5-alexander.shishkin@linux.intel.com>
Date:   Fri,  5 Jul 2019 17:14:24 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH v1 4/5] intel_th: msu: Prevent freeing buffers while locked windows exist

We already prevent freeing buffers via sysfs interface in case there are
existing users or if trace is active. Treat the existence of locked windows
similarly and return -EBUSY on attempts to free the buffer. When the last
window is unlocked, the freeing will succeed.

Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 drivers/hwtracing/intel_th/msu.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c
index a6c0eb09c515..b200d9d1c7a0 100644
--- a/drivers/hwtracing/intel_th/msu.c
+++ b/drivers/hwtracing/intel_th/msu.c
@@ -724,6 +724,11 @@ static int msc_win_set_lockout(struct msc_window *win,
 
 	win->lockout = new;
 
+	if (old == expect && new == WIN_LOCKED)
+		atomic_inc(&win->msc->user_count);
+	else if (old == expect && old == WIN_LOCKED)
+		atomic_dec(&win->msc->user_count);
+
 unlock:
 	spin_unlock_irqrestore(&win->lo_lock, flags);
 
-- 
2.20.1