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Improve sbuf(9) manual #14

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0mp opened this issue Jun 25, 2016 · 0 comments
Open

Improve sbuf(9) manual #14

0mp opened this issue Jun 25, 2016 · 0 comments
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other/freebsd-improvement

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@0mp
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0mp commented Jun 25, 2016

  1. The example code doesn't work out of the box.
  2. There is no info about -lsbuf.
  3. Dependencies lack the NULL definition used by sbuf_new_auto().
0mp pushed a commit that referenced this issue Sep 17, 2020
@DimitryAndric
Merge commit 1ce07cd614be from llvm git (by me):
66b0278 
  Instantiate Error in Target::GetEntryPointAddress() only when
  necessary

  When Target::GetEntryPointAddress() calls
  exe_module->GetObjectFile()->GetEntryPointAddress(), and the returned
  entry_addr is valid, it can immediately be returned.

  However, just before that, an llvm::Error value has been setup, but
  in this case it is not consumed before returning, like is done
  further below in the function.

  In https://bugs.freebsd.org/248745 we got a bug report for this,
  where a very simple test case aborts and dumps core:

  * thread #1, name = 'testcase', stop reason = breakpoint 1.1
      frame #0: 0x00000000002018d4 testcase`main(argc=1, argv=0x00007fffffffea18) at testcase.c:3:5
     1    int main(int argc, char *argv[])
     2    {
  -> 3        return 0;
     4    }
  (lldb) p argc
  Program aborted due to an unhandled Error:
  Error value was Success. (Note: Success values must still be checked prior to being destroyed).

  Thread 1 received signal SIGABRT, Aborted.
  thr_kill () at thr_kill.S:3
  3       thr_kill.S: No such file or directory.
  (gdb) bt
  #0  thr_kill () at thr_kill.S:3
  #1  0x00000008049a0004 in __raise (s=6) at /usr/src/lib/libc/gen/raise.c:52
  #2  0x0000000804916229 in abort () at /usr/src/lib/libc/stdlib/abort.c:67
  #3  0x000000000451b5f5 in fatalUncheckedError () at /usr/src/contrib/llvm-project/llvm/lib/Support/Error.cpp:112
  #4  0x00000000019cf008 in GetEntryPointAddress () at /usr/src/contrib/llvm-project/llvm/include/llvm/Support/Error.h:267
  #5  0x0000000001bccbd8 in ConstructorSetup () at /usr/src/contrib/llvm-project/lldb/source/Target/ThreadPlanCallFunction.cpp:67
  #6  0x0000000001bcd2c0 in ThreadPlanCallFunction () at /usr/src/contrib/llvm-project/lldb/source/Target/ThreadPlanCallFunction.cpp:114
  #7  0x00000000020076d4 in InferiorCallMmap () at /usr/src/contrib/llvm-project/lldb/source/Plugins/Process/Utility/InferiorCallPOSIX.cpp:97
  #8  0x0000000001f4be33 in DoAllocateMemory () at /usr/src/contrib/llvm-project/lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.cpp:604
  #9  0x0000000001fe51b9 in AllocatePage () at /usr/src/contrib/llvm-project/lldb/source/Target/Memory.cpp:347
  #10 0x0000000001fe5385 in AllocateMemory () at /usr/src/contrib/llvm-project/lldb/source/Target/Memory.cpp:383
  #11 0x0000000001974da2 in AllocateMemory () at /usr/src/contrib/llvm-project/lldb/source/Target/Process.cpp:2301
  #12 CanJIT () at /usr/src/contrib/llvm-project/lldb/source/Target/Process.cpp:2331
  #13 0x0000000001a1bf3d in Evaluate () at /usr/src/contrib/llvm-project/lldb/source/Expression/UserExpression.cpp:190
  #14 0x00000000019ce7a2 in EvaluateExpression () at /usr/src/contrib/llvm-project/lldb/source/Target/Target.cpp:2372
  #15 0x0000000001ad784c in EvaluateExpression () at /usr/src/contrib/llvm-project/lldb/source/Commands/CommandObjectExpression.cpp:414
  #16 0x0000000001ad86ae in DoExecute () at /usr/src/contrib/llvm-project/lldb/source/Commands/CommandObjectExpression.cpp:646
  #17 0x0000000001a5e3ed in Execute () at /usr/src/contrib/llvm-project/lldb/source/Interpreter/CommandObject.cpp:1003
  #18 0x0000000001a6c4a3 in HandleCommand () at /usr/src/contrib/llvm-project/lldb/source/Interpreter/CommandInterpreter.cpp:1762
  #19 0x0000000001a6f98c in IOHandlerInputComplete () at /usr/src/contrib/llvm-project/lldb/source/Interpreter/CommandInterpreter.cpp:2760
  #20 0x0000000001a90b08 in Run () at /usr/src/contrib/llvm-project/lldb/source/Core/IOHandler.cpp:548
  #21 0x00000000019a6c6a in ExecuteIOHandlers () at /usr/src/contrib/llvm-project/lldb/source/Core/Debugger.cpp:903
  #22 0x0000000001a70337 in RunCommandInterpreter () at /usr/src/contrib/llvm-project/lldb/source/Interpreter/CommandInterpreter.cpp:2946
  #23 0x0000000001d9d812 in RunCommandInterpreter () at /usr/src/contrib/llvm-project/lldb/source/API/SBDebugger.cpp:1169
  #24 0x0000000001918be8 in MainLoop () at /usr/src/contrib/llvm-project/lldb/tools/driver/Driver.cpp:675
  #25 0x000000000191a114 in main () at /usr/src/contrib/llvm-project/lldb/tools/driver/Driver.cpp:890

  Fix the incorrect error catch by only instantiating an Error object
  if it is necessary.

  Reviewed By: JDevlieghere

  Differential Revision: https://reviews.llvm.org/D86355

This should fix lldb aborting as described in the scenario above.

Reported by:	dmgk
PR:		248745
0mp pushed a commit that referenced this issue Apr 18, 2023
@rob-wing
FreeBSD: don't verify recycled vnode for zfs control directory
28251d8 
Under certain loads, the following panic is hit:

    panic: page fault
    KDB: stack backtrace:
    #0 0xffffffff805db025 at kdb_backtrace+0x65
    #1 0xffffffff8058e86f at vpanic+0x17f
    #2 0xffffffff8058e6e3 at panic+0x43
    #3 0xffffffff808adc15 at trap_fatal+0x385
    #4 0xffffffff808adc6f at trap_pfault+0x4f
    #5 0xffffffff80886da8 at calltrap+0x8
    #6 0xffffffff80669186 at vgonel+0x186
    #7 0xffffffff80669841 at vgone+0x31
    #8 0xffffffff8065806d at vfs_hash_insert+0x26d
    #9 0xffffffff81a39069 at sfs_vgetx+0x149
    #10 0xffffffff81a39c54 at zfsctl_snapdir_lookup+0x1e4
    #11 0xffffffff8065a28c at lookup+0x45c
    #12 0xffffffff806594b9 at namei+0x259
    #13 0xffffffff80676a33 at kern_statat+0xf3
    #14 0xffffffff8067712f at sys_fstatat+0x2f
    #15 0xffffffff808ae50c at amd64_syscall+0x10c
    #16 0xffffffff808876bb at fast_syscall_common+0xf8

The page fault occurs because vgonel() will call VOP_CLOSE() for active
vnodes. For this reason, define vop_close for zfsctl_ops_snapshot. While
here, define vop_open for consistency.

After adding the necessary vop, the bug progresses to the following
panic:

    panic: VERIFY3(vrecycle(vp) == 1) failed (0 == 1)
    cpuid = 17
    KDB: stack backtrace:
    #0 0xffffffff805e29c5 at kdb_backtrace+0x65
    #1 0xffffffff8059620f at vpanic+0x17f
    #2 0xffffffff81a27f4a at spl_panic+0x3a
    #3 0xffffffff81a3a4d0 at zfsctl_snapshot_inactive+0x40
    #4 0xffffffff8066fdee at vinactivef+0xde
    #5 0xffffffff80670b8a at vgonel+0x1ea
    #6 0xffffffff806711e1 at vgone+0x31
    #7 0xffffffff8065fa0d at vfs_hash_insert+0x26d
    #8 0xffffffff81a39069 at sfs_vgetx+0x149
    #9 0xffffffff81a39c54 at zfsctl_snapdir_lookup+0x1e4
    #10 0xffffffff80661c2c at lookup+0x45c
    #11 0xffffffff80660e59 at namei+0x259
    #12 0xffffffff8067e3d3 at kern_statat+0xf3
    #13 0xffffffff8067eacf at sys_fstatat+0x2f
    #14 0xffffffff808b5ecc at amd64_syscall+0x10c
    #15 0xffffffff8088f07b at fast_syscall_common+0xf8

This is caused by a race condition that can occur when allocating a new
vnode and adding that vnode to the vfs hash. If the newly created vnode
loses the race when being inserted into the vfs hash, it will not be
recycled as its usecount is greater than zero, hitting the above
assertion.

Fix this by dropping the assertion.

FreeBSD-issue: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=252700
Reviewed-by: Andriy Gapon <[email protected]>
Reviewed-by: Mateusz Guzik <[email protected]>
Reviewed-by: Alek Pinchuk <[email protected]>
Reviewed-by: Ryan Moeller <[email protected]>
Signed-off-by: Rob Wing <[email protected]>
Co-authored-by: Rob Wing <[email protected]>
Submitted-by: Klara, Inc.
Sponsored-by: rsync.net
Closes #14501
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