From f7bc9b209e27c0b617378400136cc663a6314d0c Mon Sep 17 00:00:00 2001 From: "Gautham R. Shenoy" Date: Tue, 7 Nov 2017 13:39:29 +0530 Subject: cpufreq: stats: Handle the case when trans_table goes beyond PAGE_SIZE On platforms with large number of Pstates, the transition table, which is a NxN matrix, can overflow beyond the PAGE_SIZE boundary. This can be seen on POWER9 which has 100+ Pstates. As a result, each time the trans_table is read for any of the CPUs, we will get the following error. --------------------------------------------------- fill_read_buffer: show+0x0/0xa0 returned bad count --------------------------------------------------- This patch ensures that in case of an overflow, we print a warning once in the dmesg and return FILE TOO LARGE error for this and all subsequent accesses of trans_table. Signed-off-by: Gautham R. Shenoy Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki --- Documentation/cpu-freq/cpufreq-stats.txt | 3 +++ 1 file changed, 3 insertions(+) (limited to 'Documentation') diff --git a/Documentation/cpu-freq/cpufreq-stats.txt b/Documentation/cpu-freq/cpufreq-stats.txt index 2bbe207354ed..a873855c811d 100644 --- a/Documentation/cpu-freq/cpufreq-stats.txt +++ b/Documentation/cpu-freq/cpufreq-stats.txt @@ -90,6 +90,9 @@ Freq_i to Freq_j. Freq_i is in descending order with increasing rows and Freq_j is in descending order with increasing columns. The output here also contains the actual freq values for each row and column for better readability. +If the transition table is bigger than PAGE_SIZE, reading this will +return an -EFBIG error. + -------------------------------------------------------------------------------- :/sys/devices/system/cpu/cpu0/cpufreq/stats # cat trans_table From : To -- cgit v1.2.3