linux: ns: get_process_nspid() support old kernels

CONTRIBUTING.md

@@ -15,7 +15,7 @@ on you machine:
 
 To get the source of `gprofiler`, clone the git repository via:
 ````bash
-git clone https://github.com/granulate/gprofiler
+git clone --recursive https://github.com/granulate/gprofiler
 ````
 
 This will clone the complete source to your local machine. Navigate to the project folder

gprofiler/profilers/java.py

@@ -25,7 +25,7 @@
     java_exit_code_to_signo,
     locate_hotspot_error_file,
 )
-from granulate_utils.linux import proc_events
+from granulate_utils.linux import proc_events, ns
 from granulate_utils.linux.ns import get_proc_root_path, resolve_proc_root_links, run_in_ns
 from granulate_utils.linux.oom import get_oom_entry
 from granulate_utils.linux.signals import get_signal_entry
@@ -41,7 +41,6 @@
 from gprofiler.profilers.registry import ProfilerArgument, register_profiler
 from gprofiler.utils import (
     TEMPORARY_STORAGE_PATH,
-    get_process_nspid,
     is_process_running,
     pgrep_maps,
     process_comm,
@@ -149,7 +148,7 @@ def __init__(
         self._process_root = get_proc_root_path(process)
         self._cmdline = process.cmdline()
         self._cwd = process.cwd()
-        self._nspid = get_process_nspid(self.process.pid)
+        self._nspid = ns.get_process_nspid(self.process.pid)
 
         # not using storage_dir for AP itself on purpose: this path should remain constant for the lifetime
         # of the target process, so AP is loaded exactly once (if we have multiple paths, AP can be loaded
@@ -217,11 +216,6 @@ def _existing_realpath(self, path: str) -> Optional[str]:
         return path if os.path.exists(path) else None
 
     def locate_hotspot_error_file(self) -> Optional[str]:
-        # nspid is required
-        if self._nspid is None:
-            # TODO: fix get_process_nspid so it always succeeds
-            return None
-
         for path in locate_hotspot_error_file(self._nspid, self._cmdline):
             realpath = self._existing_realpath(path)
             if realpath is not None:
@@ -605,23 +599,20 @@ def _is_jvm_version_supported(self, java_version_cmd_output: str) -> bool:
 
     @staticmethod
     def _get_java_version(process: Process) -> str:
-        nspid = get_process_nspid(process.pid)
-        if nspid is not None:
-            # this has the benefit of working even if the Java binary was replaced, e.g due to an upgrade.
-            # in that case, the libraries would have been replaced as well, and therefore we're actually checking
-            # the version of the now installed Java, and not the running one.
-            # but since this is used for the "JDK type" check, it's good enough - we don't expect that to change.
-            # this whole check, however, is growing to be too complex, and we should consider other approaches
-            # for it:
-            # 1. purely in async-profiler - before calling any APIs that might harm blacklisted JDKs, we can
-            #    check the JDK type in async-profiler itself.
-            # 2. assume JDK type by the path, e.g the "java" Docker image has
-            #    "/usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java" which means "OpenJDK". needs to be checked for
-            #    other JDK types.
-            java_path = f"/proc/{nspid}/exe"
-        else:
-            # TODO fix get_process_nspid() for all cases.
-            java_path = os.readlink(f"/proc/{process.pid}/exe")
+        nspid = ns.get_process_nspid(process.pid)
+
+        # this has the benefit of working even if the Java binary was replaced, e.g due to an upgrade.
+        # in that case, the libraries would have been replaced as well, and therefore we're actually checking
+        # the version of the now installed Java, and not the running one.
+        # but since this is used for the "JDK type" check, it's good enough - we don't expect that to change.
+        # this whole check, however, is growing to be too complex, and we should consider other approaches
+        # for it:
+        # 1. purely in async-profiler - before calling any APIs that might harm blacklisted JDKs, we can
+        #    check the JDK type in async-profiler itself.
+        # 2. assume JDK type by the path, e.g the "java" Docker image has
+        #    "/usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java" which means "OpenJDK". needs to be checked for
+        #    other JDK types.
+        java_path = f"/proc/{nspid}/exe"
 
         java_version_cmd_output = None
 

gprofiler/utils.py

@@ -62,20 +62,6 @@ def is_root() -> bool:
     return os.geteuid() == 0
 
 
-def get_process_nspid(pid: int) -> Optional[int]:
-    with open(f"/proc/{pid}/status") as f:
-        for line in f:
-            fields = line.split()
-            if fields[0] == "NSpid:":
-                return int(fields[-1])
-
-    # old kernel (pre 4.1) with no NSpid.
-    # TODO if needed, this can be implemented for pre 4.1, by reading all /proc/pid/sched files as
-    # seen by the PID NS; they expose the init NS PID (due to a bug fixed in 4.14~), and we can get the NS PID
-    # from the listing of those files itself.
-    return None
-
-
 libc: Optional[ctypes.CDLL] = None