On Tuesday 04 August 2015 12:27:46 Arnaldo Carvalho de Melo wrote: > Em Tue, Aug 04, 2015 at 04:44:53PM +0200, Milian Wolff escreveu: > > on ArchLinux with Linux 4.1.3, perf 4.1.0, I get: > > > > $ perf trace > > Error: No permissions to read > > /sys/kernel/debug/tracing/events/raw_syscalls/sys_(enter|exit) > > Hint: Try 'sudo mount -o remount,mode=755 /sys/kernel/debug' > > $ sudo mount -o remount,mode=755 /sys/kernel/debug > > $ perf trace > > Error: No permissions to read > > /sys/kernel/debug/tracing/events/raw_syscalls/sys_(enter|exit) > > Hint: Try 'sudo mount -o remount,mode=755 /sys/kernel/debug' > > > > This is b/c Arch uses tracefs, and running > > > > $ sudo mount -o remount,mode=755 /sys/kernel/debug/tracefs > > > > fixes the issue for me. Could someone please amend the error message? Do I > > also need to remount debugfs, or is tracefs sufficient for using more > > advanced perf tools? > > Well: > > [acme@zoo linux]$ perf trace ls > Error: No permissions to read > /sys/kernel/debug/tracing/events/raw_syscalls/sys_(enter|exit) > Hint: Try 'sudo mount -o remount,mode=755 /sys/kernel/debug' > > [acme@zoo linux]$ ls -la /sys/kernel/debug > ls: cannot open directory /sys/kernel/debug: Permission denied > [acme@zoo linux]$ > > So, I can't access debugfs, that is where the canonical mount point for > tracefs is, so the message can be read as well as: "hey, let me get to > where tracefs is".
Yes, at that point this message is correct. > Once that is done: > > [acme@zoo linux]$ sudo mount -o remount,mode=755 /sys/kernel/debug > [sudo] password for acme: > [acme@zoo linux]$ ls -la /sys/kernel/debug > total 0 > drwxr-xr-x. 32 root root 0 Aug 4 08:35 . > drwxr-xr-x. 10 root root 0 Aug 4 08:35 .. > drwxr-xr-x. 2 root root 0 Aug 4 08:35 acpi > <SNIP> > drwxr-xr-x. 2 root root 0 Aug 4 08:35 zswap > [acme@zoo linux]$ ls -la /sys/kernel/debug/tracing/ > ls: cannot open directory /sys/kernel/debug/tracing/: Permission denied > [acme@zoo linux]$ > > So, if I try: > > [acme@zoo linux]$ trace usleep 1 > Error: No permissions to read > /sys/kernel/debug/tracing/events/raw_syscalls/sys_(enter|exit) > Hint: Try 'sudo mount -o remount,mode=755 /sys/kernel/debug/tracing' This message I do not get, not even with my perf compiled from the v4.2-rc5 tag. And it is exactly what I was asking for. <snip> > I guess what fixes what you report is this cset: > > commit ab85785aa13c36440a91a8e9f7616357de411a1f > Author: Arnaldo Carvalho de Melo <a...@redhat.com> > Date: Mon Jul 6 08:51:41 2015 -0300 > > tools lib api debugfs: Check for tracefs when reporting errors > > Now that we have two mountpoints, one for debugfs and another, for > tracefs, we end up needing to check permissions for both, so, on > a system with default config we were always asking the user to > check the permission of the debugfs mountpoint, even when it was > already sufficient. Fix it. > > ----------- > > [acme@zoo linux]$ git describe ab85785aa13c36440a91a8e9f7616357de411a1f > v4.2-rc1-17-gab85785aa13c > > So, can you try running the perf tools, built from the latest 4.2-rc > codebase to see if it behaves as you expect? This is not included in 4.2-rc5 as far as I can see: $ git describe v4.2-rc5-2-ga64d3e5 $ git show ab85785aa13c36440a91a8e9f7616357de411a1f fatal: bad object ab85785aa13c36440a91a8e9f7616357de411a1f $ git log --grep debugfs --oneline --author=Arnaldo f816b3c tools lib fs debugfs: Check if debugfs is mounted when handling ENOENT ... Thanks -- Milian Wolff m...@milianw.de http://milianw.de -- To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
