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cdrom_id: retry to open the device, if EBUSY

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We might fight about the device with polling processes, or other
users who probe the device. Retry a few times if the other one goes
away in the meantime.

Based on a patch from Harald Hoyer.
This commit is contained in:
Kay Sievers 2010-04-07 09:24:25 +02:00
parent 36a07a8c34
commit cccfffbe04
1 changed files with 17 additions and 1 deletions
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18
extras/cdrom_id/cdrom_id.c
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@ -30,6 +30,7 @@
#include <fcntl.h> #include <fcntl.h>
#include <errno.h> #include <errno.h>
#include <getopt.h> #include <getopt.h>
#include <time.h>
#include <scsi/sg.h> #include <scsi/sg.h>
#include <sys/types.h> #include <sys/types.h>
#include <sys/stat.h> #include <sys/stat.h>
@ -591,7 +592,22 @@ int main(int argc, char *argv[])
goto exit; goto exit;
} }
fd = open(node, O_RDONLY|O_NONBLOCK|(is_mounted(node) ? 0 : O_EXCL)); if (is_mounted(node)) {
fd = open(node, O_RDONLY|O_NONBLOCK);
} else {
int cnt;
struct timespec duration;
srand((unsigned int)getpid());
for (cnt = 40; cnt > 0; cnt--) {
fd = open(node, O_RDONLY|O_NONBLOCK|O_EXCL);
if (fd >= 0 || errno != EBUSY)
break;
duration.tv_sec = 0;
duration.tv_nsec = (100 * 1000 * 1000) + (rand() % 100 * 1000 * 1000);
nanosleep(&duration, NULL);
}
}
if (fd < 0) { if (fd < 0) {
info(udev, "unable to open '%s'\n", node); info(udev, "unable to open '%s'\n", node);
fprintf(stderr, "unable to open '%s'\n", node); fprintf(stderr, "unable to open '%s'\n", node);