commit b22be68453b2497e86cbd273b9cd56fadc5859e3

Author: Ying Lv <lvying6@huawei.com>

Date:   Wed May 15 11:15:42 2019 +0800

    fix rasdaemon high CPU usage when part of CPUs offline

    When we set part of CPU core offline, such as by setting the kernel cmdline

    maxcpus = N(N is less than the total number of system CPU cores).

    And then, we will observe that the CPU usage of some rasdaemon threads

    is very close to 100.

    This is because when part of CPU offline, poll in read_ras_event_all_cpus func

    will fallback to pthread way.

    Offlined CPU thread will return negative value when read trace_pipe_raw,

    negative return value will covert to positive value because of 'unsigned size'.

    So code will always go into 'size > 0' branch, and the CPU usage is too high.

    Here, variable size uses int type will go to the right branch.

    Fiexs: eff7c9e0("ras-events: Only use pthreads for collect if poll() not available")

    Reported-by: Zhipeng Xie <xiezhipeng1@huawei.com>

    Signed-off-by: Ying Lv <lvying6@huawei.com>

    Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

diff --git a/ras-events.c b/ras-events.c

index 4e7b815..38ebe1e 100644

--- a/ras-events.c

+++ b/ras-events.c

@@ -426,7 +426,7 @@ static int read_ras_event(int fd,

 			  struct kbuffer *kbuf,

 			  void *page)

 {

-	unsigned size;

+	int size;

 	unsigned long long time_stamp;

 	void *data;