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win: unmask evtchn before checking if libvchan_wait is needed

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This should prevent the race, when evtchn is signalled between condition check
and libvchan_wait call.
This commit is contained in:
Marek Marczykowski 2012-08-03 02:02:26 +02:00
parent 847fe81dcd
commit ec47c5eb81
1 changed files with 12 additions and 0 deletions
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12
vchan/io.c
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@ -125,6 +125,12 @@ int libvchan_write(struct libvchan *ctrl, char *data, int size)
{
int avail, avail_contig;
int real_idx;
#ifdef WINNT
// because of mask-on-fire and do_notify called previously, evtchn must be
// unmasked before libvchan_wait. Do it before checking if data is
// available to prevent race
libvchan_prepare_to_select(ctrl);
#endif
while ((avail = libvchan_buffer_space(ctrl)) == 0)
if (libvchan_wait(ctrl) < 0)
return -1;
@ -150,6 +156,12 @@ int libvchan_read(struct libvchan *ctrl, char *data, int size)
{
int avail, avail_contig;
int real_idx;
#ifdef WINNT
// because of mask-on-fire and do_notify called previously, evtchn must be
// unmasked before libvchan_wait. Do it before checking if data is
// available to prevent race
libvchan_prepare_to_select(ctrl);
#endif
while ((avail = libvchan_data_ready(ctrl)) == 0)
if (libvchan_wait(ctrl) < 0)
return -1;