On Sun, 2018-05-20 at 14:16 +0200, Benedikt Schemmer wrote:
> There is exactly one flock in mesa and it caused mesa not to build
> on windows when shader cache was enabled.
>
> It should be possible to revert 9f8dc3bf03ec825bae7041858dda6ca2e9a34363
> "utils: build sha1/disk cache only with Android/Autoconf" currently
> guarding the offending code with ENABLE_SHADER_CACHE
>
> This would allow shader cache to work on windows I think.
>
> I dont have a test system with windows though.
> This builds on linux and is tested with Deus Ex:MD and Metro 2033 Redux
> both with cold shader cache.
>
> Really
> Fixes: d1efa09d342bff3e5def2978a0bef748d74f9c82
>
> CC: Tapani Pälli <tapani.pa...@intel.com>
> CC: "Marek Olšák" <mar...@gmail.com>
> CC: Emil Velikov <emil.l.veli...@gmail.com>
> CC: Timothy Arceri <tarc...@itsqueeze.com>
> CC: Samuel Pitoiset <samuel.pitoi...@gmail.com>
> ---
> This enables the patch
> [PATCH 1/3] mesa/main/shaderapi: Use generate_sha1() unconditionally
>
> src/util/disk_cache.c | 48 +++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 35 insertions(+), 13 deletions(-)
>
> diff --git a/src/util/disk_cache.c b/src/util/disk_cache.c
> index 4a762eff20..ca47bb15fb 100644
> --- a/src/util/disk_cache.c
> +++ b/src/util/disk_cache.c
> @@ -28,7 +28,6 @@
> #include <string.h>
> #include <stdlib.h>
> #include <stdio.h>
> -#include <sys/file.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <sys/mman.h>
> @@ -848,6 +847,29 @@ struct cache_entry_file_data {
> uint32_t uncompressed_size;
> };
>
> +static char *
> +generate_random_string(int length) {
> + static const char a[] = "0123456789abcdef";
> +
> + if (length > 16)
> + return NULL;
> +
> + char buf[16];
> + char *rndstr;
> +
> + for (int i = 0; i < length - 1; ++i) {
> + // assign a random element from the lookup table
> + buf[i] = a[rand() % (sizeof(a) - 1)];
> + }
> +
> + buf[length - 1] = 0;
> +
> + if (asprintf(&rndstr, "%s", buf) == -1)
> + return NULL;
> +
> + return rndstr;
> +}
This looks like you're trying to reimplement mktemp (also available on
windows).
> +
> static void
> cache_put(void *job, int thread_index)
> {
> @@ -855,7 +877,7 @@ cache_put(void *job, int thread_index)
>
> int fd = -1, fd_final = -1, err, ret;
> unsigned i = 0;
> - char *filename = NULL, *filename_tmp = NULL;
> + char *filename = NULL, *filename_tmp = NULL, *random = NULL;
> struct disk_cache_put_job *dc_job = (struct disk_cache_put_job *) job;
>
> filename = get_cache_file(dc_job->cache, dc_job->key);
> @@ -873,7 +895,16 @@ cache_put(void *job, int thread_index)
> * final destination filename, (to prevent any readers from seeing
> * a partially written file).
> */
> - if (asprintf(&filename_tmp, "%s.tmp", filename) == -1)
> +
> + /* This next part used to be an flock(), which would prevent windows
> systems
> + * to build. 4 hex characters should be enough to prevent filename race
> + * conditions for now.
> + */
> + random = generate_random_string(4);
> + if (random == NULL)
> + goto done;
> +
> + if (asprintf(&filename_tmp, "%s_%s.tmp", filename, random) == -1)
> goto done;
>
> fd = open(filename_tmp, O_WRONLY | O_CLOEXEC | O_CREAT, 0644);
> @@ -890,16 +921,7 @@ cache_put(void *job, int thread_index)
> goto done;
> }
you can avoid the lock if you use O_CREAT | O_EXCL. The thread that
looses race will receive EEXIST error from the open() call. It should
also work on windows.
Jan
>
> - /* With the temporary file open, we take an exclusive flock on
> - * it. If the flock fails, then another process still has the file
> - * open with the flock held. So just let that file be responsible
> - * for writing the file.
> - */
> - err = flock(fd, LOCK_EX | LOCK_NB);
> - if (err == -1)
> - goto done;
> -
> - /* Now that we have the lock on the open temporary file, we can
> + /* Now that we have the open temporary file, we can
> * check to see if the destination file already exists. If so,
> * another process won the race between when we saw that the file
> * didn't exist and now. In this case, we don't do anything more,
--
Jan Vesely <jan.ves...@rutgers.edu>
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