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Bug #861

closed

UST subbuffers silently dropped on moderate trace traffic

Added by Mathieu Desnoyers about 10 years ago. Updated about 10 years ago.

Status:
Resolved
Priority:
Critical
Assignee:
Mathieu Desnoyers
Target version:
LTTng - 2.4
Start date:
11/18/2014
Due date:
% Done:

100%

Estimated time:

Description

lttng-tools commit 02b3d1769d5f8a33e4109b1e681141c9295dfda6 introduced an important regression for lttng-ust tracing in the consumer daemon: after reading a sub-buffer, a check has been added to see whether there are more sub-buffers available to read, and if it is the case, it ensures the wakeup pipe will be awakened again.

The issue lies in the use of ustctl_put_next_subbuf() in this check. This acts as if the sub-buffer has been read, when in reality it has not been read. It therefore trashes the data contained by this sub-buffer.

This check should use ustctl_put_subbuf(), which does not move the consumer position.

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 #1

Updated by Mathieu Desnoyers about 10 years ago

  • Status changed from Confirmed to Resolved
  • % Done changed from 0 to 100

Applied in changeset tools|commit:5420e5dbd5fd06f2d1ba524d44eed601daef792c.

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