mainlining shenanigans
a18ee796f8
There's a problem with relying on backtrace data from 'perf trace' the way the trace+probe_libc_inet_pton does. This test inserts uprobe within ping binary and checks that it gets its sample using 'perf trace'. It also checks it gets proper backtrace from sample and that's where the issue is. The 'perf trace' does not sort events (by definition) so it can happen that it processes the event sample before the ping binary memory map event. This can (very rarely) happen as proved by this events dump output (from custom added debug output): ... 7680/7680: [0x7f4e29718000(0x204000) @ 0 fd:00 33611321 4230892504]: r-xp /usr/lib64/libdl-2.17.so 7680/7680: [0x7f4e29502000(0x216000) @ 0 fd:00 33617257 2606846872]: r-xp /usr/lib64/libz.so.1.2.7 (IP, 0x2): 7680/7680: 0x7f4e29c2ed60 period: 1 addr: 0 7680/7680: [0x564842ef0000(0x233000) @ 0 fd:00 83 1989280200]: r-xp /usr/bin/ping 7680/7680: [0x7f4e2aca2000(0x224000) @ 0 fd:00 33611308 1219144940]: r-xp /usr/lib64/ld-2.17.so ... In this case 'perf trace' fails to resolve the last callchain IP (within the ping binary) because it does not know about the ping binary memory map yet and the test fails like this: PING ::1(::1) 56 data bytes 64 bytes from ::1: icmp_seq=1 ttl=64 time=0.037 ms --- ::1 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 0.037/0.037/0.037/0.000 ms 0.000 probe_libc:inet_pton:(7f4e29c2ed60)) __GI___inet_pton (/usr/lib64/libc-2.17.so) getaddrinfo (/usr/lib64/libc-2.17.so) [0] ([unknown]) FAIL: expected backtrace entry 8 ".*\(.*/bin/ping.*\)$" got "[0] ([unknown])" Switching the test to use 'perf record' and 'perf script' instead of 'perf trace'. Signed-off-by: Jiri Olsa <jolsa@kernel.org> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: David Ahern <dsahern@gmail.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20180301165215.6780-1-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.