From: naveen.n.rao at linux.vnet.ibm.com (Naveen N. Rao) Subject: [PATCH v7 00/16] tracing: probeevent: Improve fetcharg features Date: Tue, 08 May 2018 15:41:11 +0530 [thread overview] Message-ID: <1525772835.npvwj0nws0.naveen@linux.ibm.com> (raw) In-Reply-To: <20180507235317.fa04131c603dbe59ef78a829@kernel.org> Masami Hiramatsu wrote: > On Mon, 07 May 2018 13:41:53 +0530 > "Naveen N. Rao" <naveen.n.rao at linux.vnet.ibm.com> wrote: >> >> >> >> I didn't understand that. Which code are you planning to remove? Can you >> >> please elaborate? I thought we still need to disable preemption in the >> >> ftrace handler. >> > >> > Yes, kprobe_ftrace_handler itself must be run under preempt disabled >> > because it depends on a per-cpu variable. What I will remove is the >> > redundant preempt disable/enable_noresched (unbalanced) pair in the >> > kprobe_ftrace_handler, and jprobe x86 ports which is no more used. >> >> Won't that break out-of-tree users depending on returning a non-zero >> value to handle preemption differently? You seem to have alluded to it >> earlier in the mail chain above where you said that this is not just for >> jprobes (though it was added for jprobes as the main use case). > > No, all users are in tree already (function override for bpf and error-injection). Ok, so BPF error injection is a new user that can return a non-zero value from the pre handler. It looks like it can use KPROBES_ON_FTRACE too. In that case, on function entry, we call into kprobe_ftrace_handler() which will call fei_kprobe_handler(), which can re-enable premption before returning 1. So, if you remove the additional prempt_disable()/enable_no_resched() in kprobe_ftrace_handler(), then it will become imbalanced, right? > And also, for changing execution path by using kprobes, user handler must call > not only preempt_enable(), but also clear current_kprobe per-cpu variable which > is not exported to kmodules. Ok, good point. And that means we don't have any external users any more. Thanks, Naveen -- To unsubscribe from this list: send the line "unsubscribe linux-kselftest" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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From: naveen.n.rao@linux.vnet.ibm.com (Naveen N. Rao) Subject: [PATCH v7 00/16] tracing: probeevent: Improve fetcharg features Date: Tue, 08 May 2018 15:41:11 +0530 [thread overview] Message-ID: <1525772835.npvwj0nws0.naveen@linux.ibm.com> (raw) Message-ID: <20180508101111.nAs-lkkrtBL8Rd74bL7SAdZyy-9TZmg6Tzq7rlrJ_Ag@z> (raw) In-Reply-To: <20180507235317.fa04131c603dbe59ef78a829@kernel.org> Masami Hiramatsu wrote: > On Mon, 07 May 2018 13:41:53 +0530 > "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote: >> >> >> >> I didn't understand that. Which code are you planning to remove? Can you >> >> please elaborate? I thought we still need to disable preemption in the >> >> ftrace handler. >> > >> > Yes, kprobe_ftrace_handler itself must be run under preempt disabled >> > because it depends on a per-cpu variable. What I will remove is the >> > redundant preempt disable/enable_noresched (unbalanced) pair in the >> > kprobe_ftrace_handler, and jprobe x86 ports which is no more used. >> >> Won't that break out-of-tree users depending on returning a non-zero >> value to handle preemption differently? You seem to have alluded to it >> earlier in the mail chain above where you said that this is not just for >> jprobes (though it was added for jprobes as the main use case). > > No, all users are in tree already (function override for bpf and error-injection). Ok, so BPF error injection is a new user that can return a non-zero value from the pre handler. It looks like it can use KPROBES_ON_FTRACE too. In that case, on function entry, we call into kprobe_ftrace_handler() which will call fei_kprobe_handler(), which can re-enable premption before returning 1. So, if you remove the additional prempt_disable()/enable_no_resched() in kprobe_ftrace_handler(), then it will become imbalanced, right? > And also, for changing execution path by using kprobes, user handler must call > not only preempt_enable(), but also clear current_kprobe per-cpu variable which > is not exported to kmodules. Ok, good point. And that means we don't have any external users any more. Thanks, Naveen -- To unsubscribe from this list: send the line "unsubscribe linux-kselftest" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2018-05-08 10:11 UTC|newest] Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-04-25 12:16 [PATCH v7 00/16] tracing: probeevent: Improve fetcharg features mhiramat 2018-04-25 12:16 ` Masami Hiramatsu 2018-04-25 12:16 ` [PATCH v7 01/16] tracing: probeevent: Cleanup print argument functions mhiramat 2018-04-25 12:16 ` Masami Hiramatsu 2018-04-25 12:17 ` [PATCH v7 02/16] tracing: probeevent: Cleanup argument field definition mhiramat 2018-04-25 12:17 ` Masami Hiramatsu 2018-04-25 12:17 ` [PATCH v7 03/16] tracing: probeevent: Remove NOKPROBE_SYMBOL from print functions mhiramat 2018-04-25 12:17 ` Masami Hiramatsu 2018-04-25 12:18 ` [PATCH v7 04/16] tracing: probeevent: Introduce new argument fetching code mhiramat 2018-04-25 12:18 ` Masami Hiramatsu 2018-04-25 12:18 ` [PATCH v7 05/16] tracing: probeevent: Unify fetch type tables mhiramat 2018-04-25 12:18 ` Masami Hiramatsu 2018-04-25 12:19 ` [PATCH v7 06/16] tracing: probeevent: Return consumed bytes of dynamic area mhiramat 2018-04-25 12:19 ` Masami Hiramatsu 2018-04-25 12:19 ` [PATCH v7 07/16] tracing: probeevent: Append traceprobe_ for exported function mhiramat 2018-04-25 12:19 ` Masami Hiramatsu 2018-04-25 12:19 ` [PATCH v7 08/16] tracing: probeevent: Unify fetch_insn processing common part mhiramat 2018-04-25 12:19 ` Masami Hiramatsu 2018-04-25 12:20 ` [PATCH v7 09/16] tracing: probeevent: Add symbol type mhiramat 2018-04-25 12:20 ` Masami Hiramatsu 2018-04-25 12:20 ` [PATCH v7 10/16] x86: ptrace: Add function argument access API mhiramat 2018-04-25 12:20 ` Masami Hiramatsu 2018-04-25 12:21 ` [PATCH v7 11/16] tracing: probeevent: Add $argN for accessing function args mhiramat 2018-04-25 12:21 ` Masami Hiramatsu 2018-04-25 12:21 ` [PATCH v7 12/16] tracing: probeevent: Add array type support mhiramat 2018-04-25 12:21 ` Masami Hiramatsu 2018-04-25 12:22 ` [PATCH v7 13/16] selftests: ftrace: Add a testcase for symbol type mhiramat 2018-04-25 12:22 ` Masami Hiramatsu 2018-04-25 12:22 ` [PATCH v7 14/16] selftests: ftrace: Add a testcase for $argN with kprobe_event mhiramat 2018-04-25 12:22 ` Masami Hiramatsu 2018-04-25 12:23 ` [PATCH v7 15/16] selftests: ftrace: Add a testcase for array type " mhiramat 2018-04-25 12:23 ` Masami Hiramatsu 2018-04-25 12:23 ` [PATCH v7 16/16] perf-probe: Add array argument support mhiramat 2018-04-25 12:23 ` Masami Hiramatsu 2018-04-27 1:42 ` [PATCH v7 00/16] tracing: probeevent: Improve fetcharg features rostedt 2018-04-27 1:42 ` Steven Rostedt 2018-05-03 22:11 ` rostedt 2018-05-03 22:11 ` Steven Rostedt 2018-05-04 15:48 ` mhiramat 2018-05-04 15:48 ` Masami Hiramatsu 2018-05-04 16:06 ` rostedt 2018-05-04 16:06 ` Steven Rostedt 2018-05-04 17:30 ` naveen.n.rao 2018-05-04 17:30 ` Naveen N. Rao 2018-05-05 2:38 ` mhiramat 2018-05-05 2:38 ` Masami Hiramatsu 2018-05-05 7:46 ` naveen.n.rao 2018-05-05 7:46 ` Naveen N. Rao 2018-05-05 14:32 ` mhiramat 2018-05-05 14:32 ` Masami Hiramatsu 2018-05-07 8:11 ` naveen.n.rao 2018-05-07 8:11 ` Naveen N. Rao 2018-05-07 14:53 ` mhiramat 2018-05-07 14:53 ` Masami Hiramatsu 2018-05-08 10:11 ` naveen.n.rao [this message] 2018-05-08 10:11 ` Naveen N. Rao 2018-05-08 15:02 ` mhiramat 2018-05-08 15:02 ` Masami Hiramatsu 2018-05-08 18:01 ` naveen.n.rao 2018-05-08 18:01 ` Naveen N. Rao 2018-05-05 15:51 ` mhiramat 2018-05-05 15:51 ` Masami Hiramatsu 2018-05-07 15:30 ` rostedt 2018-05-07 15:30 ` Steven Rostedt 2018-05-08 4:01 ` mhiramat 2018-05-08 4:01 ` Masami Hiramatsu 2018-05-07 15:21 ` rostedt 2018-05-07 15:21 ` Steven Rostedt 2018-06-21 20:16 ` rostedt 2018-06-21 20:16 ` Steven Rostedt 2018-06-22 6:04 ` mhiramat 2018-06-22 6:04 ` Masami Hiramatsu
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