[Bug bpf/24812] New: stapbpf: support order-parametrized begin/end probes

[Bug bpf/24812] New: stapbpf: support order-parametrized begin/end probes

[me at serhei dot io]

https://sourceware.org/bugzilla/show_bug.cgi?id=24812

            Bug ID: 24812
           Summary: stapbpf: support order-parametrized begin/end probes
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: bpf
          Assignee: systemtap at sourceware dot org
          Reporter: me at serhei dot io
  Target Milestone: ---

found this while trying to work around probe size requirement
-- so this will be important for complex bpf programs until/unless we bump the
userspace interpreter's stack size

I want two end probes to run in a specific order. Normally begin/end probe
order is unspecified but in fact you can constrain it with sequence numbers.

global flag1 = 0                                                                
global flag2 = 0                                                                

probe begin(1) {                                                                
  printf("BEGIN\n")                                                             
  flag1 = 2                                                                     
}                                                                               

probe begin(2) {                                                                
  flag1 = 1                                                                     
  exit()                                                                        
}                                                                               

probe end(1) {                                                                  
  flag2 = 2                                                                     
}                                                                               

probe end(2) {                                                                  
  flag2 = 1                                                                     
}                                                                               

probe end(3) {                                                                  
  printf("got flag1==%d flag2==%d\n", flag1, flag2)                             
  if (flag1 == 1 && flag2 == 1)                                                 
    printf("END PASS\n")                                                        
  else                                                                          
    printf("END FAIL\n")                                                        
}                                                                               

but it doesn't work on bpf.
$ sudo ~/stap-install/bin/stap probe_order.stp 
BEGIN
got flag1==1 flag2==1
END PASS

$ sudo ~/stap-install/bin/stap --bpf probe_order.stp 
BEGIN
got flag1==1 flag2==0
END FAIL

Mirrors pr3624 for the kernel backend.

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[Bug bpf/24812] stapbpf: support order-parametrized begin/end probes

[sapatel at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=24812

Sagar Patel <sapatel at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sapatel at redhat dot com
           Assignee|systemtap at sourceware dot org    |sapatel at redhat dot com

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