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[Bug 1001437] New: ADC HW drivers have race condition incyg_io_set_config(CYG_IO_SET_CONFIG_ADC_[EN|DIS]ABLE)
- From: bugzilla-daemon at bugs dot ecos dot sourceware dot org
- To: unassigned at bugs dot ecos dot sourceware dot org
- Date: Mon, 2 Jan 2012 16:34:34 +0000
- Subject: [Bug 1001437] New: ADC HW drivers have race condition incyg_io_set_config(CYG_IO_SET_CONFIG_ADC_[EN|DIS]ABLE)
- Auto-submitted: auto-generated
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Summary: ADC HW drivers have race condition in
cyg_io_set_config(CYG_IO_SET_CONFIG_ADC_[EN|DIS]ABLE)
Product: eCos
Version: CVS
Platform: All
OS/Version: All
Status: UNCONFIRMED
Severity: major
Priority: low
Component: ADC
AssignedTo: unassigned@bugs.ecos.sourceware.org
ReportedBy: bernard.fouche@kuantic.com
CC: ecos-bugs@ecos.sourceware.org
Class: Advice Request
Hello.
While looking at the source code of the LPC2XXX ADC driver, and after having
checked other ADC hardware drivers, it seems that all of these drivers, when
processing CYG_IO_SET_CONFIG_ADC_ENABLE and CYG_IO_SET_CONFIG_ADC_DISABLE, do
the following processing:
xxx_adc_disable(cyg_adc_channel *chan)
{
xxx_adc_info *info=chan->device->dev_priv;
...
info->chan_mask &= [some code to get bit value for concerned channel];
...
}
The opposite, for xxx_adc_enable(), is done with "info->chan_mask |= ..."
In multi-thread, if more than one thread handle ADC channels, since
info->chan_mask points, for all channels, to the same data area, then a thread
may be interrupted in the middle of the read-modify-write operation to update
the bit/channel field. Another thread can be scheduled and do its own
read-modify-write op on the same area.
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