On 09/03/2018 10:54, Alex Kiernan wrote: > On Thu, Mar 8, 2018 at 5:04 PM, Stefano Babic <[email protected]> wrote: >> Hi alex, >> >> On 08/03/2018 12:52, Alex Kiernan wrote: >>> If the U-Boot environment is stored in a regular file and redundant >>> operation isn't set, then write to a temporary file and perform an >>> atomic rename. >>> >> >> Even if it is not explicitely set (IMHO it should), this code can >> be used as library and linked to own application. That means that >> concurrency can happens. I mean: >> > > At this point you're writing the new environment, so we should hold a > lock to avoid concurrent writes.
This is already done, even if not in the way I like. tools/env/fw_env_main.c calls flock() to acquire the resource. This works using fw_printenv / fw_setenv, but not as library. Library's users as me have to provide themselves a lock before calling the fw_* functions. > >>> Signed-off-by: Alex Kiernan <[email protected]> >>> --- >>> >>> tools/env/fw_env.c | 81 >>> ++++++++++++++++++++++++++++++++++++++++++++++++++++-- >>> 1 file changed, 78 insertions(+), 3 deletions(-) >>> >>> diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c >>> index 2df3504..b814c4e 100644 >>> --- a/tools/env/fw_env.c >>> +++ b/tools/env/fw_env.c >>> @@ -14,6 +14,7 @@ >>> #include <errno.h> >>> #include <env_flags.h> >>> #include <fcntl.h> >>> +#include <libgen.h> >>> #include <linux/fs.h> >>> #include <linux/stringify.h> >>> #include <ctype.h> >>> @@ -1229,9 +1230,46 @@ static int flash_read (int fd) >>> return 0; >>> } >>> >>> +static int flash_open_tempfile(const char **dname, const char >>> **target_temp) >>> +{ >>> + char *dup_name = strdup(DEVNAME (dev_current)); >>> + char *temp_name = NULL; >>> + int rc = -1; >>> + >>> + if (!dup_name) >>> + return -1; >>> + >>> + *dname = dirname(dup_name); >>> + if (!*dname) >>> + goto err; >>> + >>> + rc = asprintf(&temp_name, "%s/uboot.tmp", *dname); >> >> Filename is fixed - should we not use mkstemp ? >> > > I went round all the temp functions before in the end deciding to fix > it. However it looks like I totally misread the contract that mkstemp > delivers - I'd thought it didn't pass you the name back, but it > clearly does; I'll go update it. > Best regards, Stefano Babic -- ===================================================================== DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: +49-8142-66989-53 Fax: +49-8142-66989-80 Email: [email protected] ===================================================================== _______________________________________________ U-Boot mailing list [email protected] https://lists.denx.de/listinfo/u-boot
