Messages in this thread Patch in this message | | | Date | Wed, 31 Oct 2018 15:06:22 +0000 | Subject | [PATCH] Document /proc/pid PID reuse behavior | From | Daniel Colascione <> |
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State explicitly that holding a /proc/pid file descriptor open does not reserve the PID. Also note that in the event of PID reuse, these open file descriptors refer to the old, now-dead process, and not the new one that happens to be named the same numeric PID. --- Documentation/filesystems/proc.txt | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 12a5e6e693b6..567f66a8a23c 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -214,6 +214,14 @@ asynchronous manner and the value may not be very precise. To see a precise snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. It's slow but very precise. +Note that an open a file descriptor to /proc/<pid> or to any of its +contained files or subdirectories does not prevent <pid> being reused +for some other process in the event that <pid> exits. Operations on +open /proc/<pid> file descriptors corresponding to dead processes +never act on any new process that the kernel may, through chance, have +also assigned the process ID <pid>. Instead, operations on these FDs +usually fail with ESRCH. + Table 1-2: Contents of the status files (as of 4.8) .............................................................................. Field Content -- 2.19.1.568.g152ad8e336-goog
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