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Cc: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
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Subject: Php-fpm will crash when perf runs with call graph option
Date: Mon, 25 Dec 2017 07:58:43 +0100
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From: yuzhoujian <yuzhoujian@didichuxing.com>

I use perf to analyze the performance overhead for the server. 
There are several dockers in the server. The php-fpm in the docker
will crash as long as the perf collects samples for all the cpus with call graph option(perf record -ag). Below is the stack trace
in the coredump.

#0  0x00007f044ff447bd in re_compile_fastmap_iter (bufp=0x7f044ff447bd <re_compile_fastmap_iter+1165>, 
		    fastmap=0x46 <Address 0x46 out of bounds>, init_state=<optimized out>, init_state=<optimized out>) at regcomp.c:407
407			      if (__wcrtomb (buf, towlower (cset->mbchars[i]), &state)
		(gdb) bt
#0  0x00007f044ff447bd in re_compile_fastmap_iter (bufp=0x7f044ff447bd <re_compile_fastmap_iter+1165>, 
	    fastmap=0x46 <Address 0x46 out of bounds>, init_state=<optimized out>, init_state=<optimized out>) at regcomp.c:407
#1  0x0000000000831160 in virtual_file_ex (state=0x7fff9c1a4f70, path=<optimized out>, verify_path=0x0, use_realpath=1)
		    at /home/xiaoju/phpng/php-7.0.6/Zend/zend_virtual_cwd.c:1335
#2  0x00000000007aacee in expand_filepath_with_mode (
	    filepath=0x7f044d6020d8 "/home/xiaoju/ep/as/store//toggles/beatles_api_discovery_is_open_by_app", 
	        real_path=0x7fff9c1a4fc0 "\360X\032\234\377\177", relative_to=<optimized out>, relative_to_len=0, realpath_mode=1)
		        at /home/xiaoju/phpng/php-7.0.6/main/fopen_wrappers.c:812
#3  0x00000000007c1536 in _php_stream_fopen (
	    filename=0x7f044d6020d8 "/home/xiaoju/ep/as/store//toggles/beatles_api_discovery_is_open_by_app", mode=0xdbb1f1 "rb", 
	        opened_path=0x0, options=0) at /home/xiaoju/phpng/php-7.0.6/main/streams/plain_wrapper.c:970
#4  0x00000000007bd084 in _php_stream_open_wrapper_ex (
	    path=0x7f044d6020d8 "/home/xiaoju/ep/as/store//toggles/beatles_api_discovery_is_open_by_app", mode=0xdbb1f1 "rb", options=8, 
	        opened_path=0x0, context=0x7f044d65f4c0) at /home/xiaoju/phpng/php-7.0.6/main/streams/streams.c:2060
#5  0x000000000071722b in zif_file_get_contents (execute_data=<optimized out>, return_value=0x7f044d615540)
			    at /home/xiaoju/phpng/php-7.0.6/ext/standard/file.c:544
#6  0x000000000065387c in phar_file_get_contents (execute_data=0x7f044d615570, return_value=0x7f044d615540)
			        at /home/xiaoju/phpng/php-7.0.6/ext/phar/func_interceptors.c:224))

I add some output info in the php source code, and found that virtual_file_ex functions's rbp value is really strange,etc 0x1, 0x31. I guess when the perf collects samples for all the cpus with -g option, it may destroy the php-fpm's stack. When the perf is running without -g option, the php-fpm is normal. Who have ever encountered similar problems?

BTW, OS in the server: Centos7.3  , Kernel version: 3.10.0-514.16.1.el7.x86_64. php-fpm version: 7.0.6 
Processor info: Intel(R) Xeon(R) CPU E5-2620 v3 @ 2.40GHz