From: Zhi Jin <zhi.jin@intel.com>
To: alexander.shishkin@linux.intel.com
Cc: linux-kernel@vger.kernel.org, Zhi Jin <zhi.jin@intel.com>
Subject: [PATCH] stm class: increase pos if no free channels found
Date: Thu, 6 Sep 2018 15:22:10 +0800 [thread overview]
Message-ID: <1536218530-18601-1-git-send-email-zhi.jin@intel.com> (raw)
Considering this case in find_free_channels():
bitmap:
+------------------+-+-+-+-+-+-+-+-+-+-+
| ...... |0|0|0|0|0|0|0|1|0|0|
+------------------+-+-+-+-+-+-+-+-+-+-+
1. Channel #2 has been occupied, so bit #2 is 1, and the others
are all 0.
2. Another thread tries to find 4 free channels from #0.
3. In the 1st loop, pos starts from 0, and then it checks if the
following 4 bits are all 0, but fails, as bit#2 is 1.
4. In the 2st loop, pos is not updated, and still starts from 0,
so nothing changes against loop #1.
5. Dead loop ...
This patch is to update the pos in step #3 to avoid the issue.
Fixes: 7bd1d4093c2f ("stm class: Introduce an abstraction for System Trace Module devices")
Signed-off-by: Zhi Jin <zhi.jin@intel.com>
---
drivers/hwtracing/stm/core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index 10bcb5d73f90..c86a979b9bd7 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -244,6 +244,8 @@ static int find_free_channels(unsigned long *bitmap, unsigned int start,
;
if (i == width)
return pos;
+
+ pos += i;
}
return -1;
--
2.7.4
next reply other threads:[~2018-09-06 7:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-06 7:22 Zhi Jin [this message]
2018-10-12 5:36 ` [PATCH] stm class: increase pos if no free channels found Jin, Zhi
2018-10-15 7:42 ` Alexander Shishkin
2018-10-15 8:16 ` Jin, Zhi
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