From a6572f84c5b135d9b6df279ed3c8de028bd1edd9 Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Fri, 17 May 2013 10:31:04 +0800 Subject: watchdog: Disallow setting watchdog_thresh to -1 In old kernels, it's allowed to set softlockup_thresh to -1 or 0 to disable softlockup detection. However watchdog_thresh only uses 0 to disable detection, and setting it to -1 just froze my box and nothing I can do but reboot. Signed-off-by: Li Zefan Acked-by: Don Zickus Link: http://lkml.kernel.org/r/51959668.9040106@huawei.com Signed-off-by: Ingo Molnar --- kernel/sysctl.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'kernel/sysctl.c') diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 9edcf456e0f..b0a1f99907f 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -120,7 +120,6 @@ extern int blk_iopoll_enabled; /* Constants used for minimum and maximum */ #ifdef CONFIG_LOCKUP_DETECTOR static int sixty = 60; -static int neg_one = -1; #endif static int zero; @@ -814,7 +813,7 @@ static struct ctl_table kern_table[] = { .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dowatchdog, - .extra1 = &neg_one, + .extra1 = &zero, .extra2 = &sixty, }, { -- cgit v1.2.3-18-g5258 From 14c63f17b1fde5a575a28e96547a22b451c71fb5 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 21 Jun 2013 08:51:36 -0700 Subject: perf: Drop sample rate when sampling is too slow This patch keeps track of how long perf's NMI handler is taking, and also calculates how many samples perf can take a second. If the sample length times the expected max number of samples exceeds a configurable threshold, it drops the sample rate. This way, we don't have a runaway sampling process eating up the CPU. This patch can tend to drop the sample rate down to level where perf doesn't work very well. *BUT* the alternative is that my system hangs because it spends all of its time handling NMIs. I'll take a busted performance tool over an entire system that's busted and undebuggable any day. BTW, my suspicion is that there's still an underlying bug here. Using the HPET instead of the TSC is definitely a contributing factor, but I suspect there are some other things going on. But, I can't go dig down on a bug like that with my machine hanging all the time. Signed-off-by: Dave Hansen Acked-by: Peter Zijlstra Cc: paulus@samba.org Cc: acme@ghostprotocols.net Cc: Dave Hansen [ Prettified it a bit. ] Signed-off-by: Ingo Molnar --- kernel/sysctl.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'kernel/sysctl.c') diff --git a/kernel/sysctl.c b/kernel/sysctl.c index b0a1f99907f..4ce13c3cedb 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1043,6 +1043,15 @@ static struct ctl_table kern_table[] = { .mode = 0644, .proc_handler = perf_proc_update_handler, }, + { + .procname = "perf_cpu_time_max_percent", + .data = &sysctl_perf_cpu_time_max_percent, + .maxlen = sizeof(sysctl_perf_cpu_time_max_percent), + .mode = 0644, + .proc_handler = perf_cpu_time_max_percent_handler, + .extra1 = &zero, + .extra2 = &one_hundred, + }, #endif #ifdef CONFIG_KMEMCHECK { -- cgit v1.2.3-18-g5258