threads / patch / 35591

patchgc: notice gc processes run by other users

Subject: [PATCH] gc: notice gc processes run by other users

## tl;dr

5 messages between Dec 31, 2013 and Jan 3, 2014. Diffs are folded; open one to read it.

replies: 4people: 5as markdown or json

Kyle J. McKay· Dec 31, 2013, 12:07 UTC · lore

Since 64a99eb4 git gc refuses to run without the --force option if another gc process on the same repository is already running.

However, if the repository is shared and user A runs git gc on the repository and while that gc is still running user B runs git gc on the same repository the gc process run by user A will not be noticed and the gc run by user B will go ahead and run.

The problem is that the kill(pid, 0) test fails with an EPERM error since user B is not allowed to signal processes owned by user A (unless user B is root).

Update the test to recognize an EPERM error as meaning the process exists and another gc should not be run (unless --force is given). ---

I suggest this be included in maint as others may also have expected the shared repository, different user gc scenario to be caught by the new code when in fact it's not without this patch.

 builtin/gc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
Show changes to builtin/gc.c +1 −1
diff --git a/builtin/gc.c b/builtin/gc.c
index c14190f8..25f2237c 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -222,7 +222,7 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
 			time(NULL) - st.st_mtime <= 12 * 3600 &&
 			fscanf(fp, "%"PRIuMAX" %127c", &pid, locking_host) == 2 &&
 			/* be gentle to concurrent "gc" on remote hosts */
-			(strcmp(locking_host, my_host) || !kill(pid, 0));
+			(strcmp(locking_host, my_host) || !kill(pid, 0) || errno == EPERM);
 		if (fp != NULL)
 			fclose(fp);
 		if (should_exit) {

-- 
1.8.5.2
Duy Nguyen· Dec 31, 2013, 13:46 UTC · re: Kyle J. McKay · lore

Re: [PATCH] gc: notice gc processes run by other users

On Tue, Dec 31, 2013 at 7:07 PM, Kyle J. McKay <mackyle@gmail.com> wrote:
Show 14 quoted lines
> Since 64a99eb4 git gc refuses to run without the --force option if
> another gc process on the same repository is already running.
>
> However, if the repository is shared and user A runs git gc on the
> repository and while that gc is still running user B runs git gc on
> the same repository the gc process run by user A will not be noticed
> and the gc run by user B will go ahead and run.
>
> The problem is that the kill(pid, 0) test fails with an EPERM error
> since user B is not allowed to signal processes owned by user A
> (unless user B is root).
>
> Update the test to recognize an EPERM error as meaning the process
> exists and another gc should not be run (unless --force is given).

Ack. Looking at kill(2) the other errors are EINVAL and ESRCH, which are fine to ignore.

Show 25 quoted lines
> ---
>
> I suggest this be included in maint as others may also have expected the
> shared repository, different user gc scenario to be caught by the new
> code when in fact it's not without this patch.
>
>  builtin/gc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/builtin/gc.c b/builtin/gc.c
> index c14190f8..25f2237c 100644
> --- a/builtin/gc.c
> +++ b/builtin/gc.c
> @@ -222,7 +222,7 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
>                         time(NULL) - st.st_mtime <= 12 * 3600 &&
>                         fscanf(fp, "%"PRIuMAX" %127c", &pid, locking_host) == 2 &&
>                         /* be gentle to concurrent "gc" on remote hosts */
> -                       (strcmp(locking_host, my_host) || !kill(pid, 0));
> +                       (strcmp(locking_host, my_host) || !kill(pid, 0) || errno == EPERM);
>                 if (fp != NULL)
>                         fclose(fp);
>                 if (should_exit) {
> --
> 1.8.5.2
>
-- 
Duy
Thiago Farina· Dec 31, 2013, 20:35 UTC · re: Kyle J. McKay · lore

Re: [PATCH] gc: notice gc processes run by other users

On Tue, Dec 31, 2013 at 10:07 AM, Kyle J. McKay <mackyle@gmail.com> wrote:
Show 14 quoted lines
> Since 64a99eb4 git gc refuses to run without the --force option if
> another gc process on the same repository is already running.
>
> However, if the repository is shared and user A runs git gc on the
> repository and while that gc is still running user B runs git gc on
> the same repository the gc process run by user A will not be noticed
> and the gc run by user B will go ahead and run.
>
> The problem is that the kill(pid, 0) test fails with an EPERM error
> since user B is not allowed to signal processes owned by user A
> (unless user B is root).
>
> Update the test to recognize an EPERM error as meaning the process
> exists and another gc should not be run (unless --force is given).
Looks like you are missing your Signed-off-by: line.

-- Thiago Farina

Kyle· Jan 3, 2014, 00:11 UTC · re: Kyle J. McKay · lore

Re: [PATCH] gc: notice gc processes run by other users

On Dec 31, 2013, at 04:07, Kyle J. McKay wrote:
Show 14 quoted lines
> Since 64a99eb4 git gc refuses to run without the --force option if
> another gc process on the same repository is already running.
>
> However, if the repository is shared and user A runs git gc on the
> repository and while that gc is still running user B runs git gc on
> the same repository the gc process run by user A will not be noticed
> and the gc run by user B will go ahead and run.
>
> The problem is that the kill(pid, 0) test fails with an EPERM error
> since user B is not allowed to signal processes owned by user A
> (unless user B is root).
>
> Update the test to recognize an EPERM error as meaning the process
> exists and another gc should not be run (unless --force is given).
Oops, sorry, forgot sign off, here's my sign off:
Signed-off-by: Kyle J. McKay <mackyle@gmail.com>
Show 28 quoted lines
> ---
>
> I suggest this be included in maint as others may also have expected  
> the
> shared repository, different user gc scenario to be caught by the new
> code when in fact it's not without this patch.
>
> builtin/gc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/builtin/gc.c b/builtin/gc.c
> index c14190f8..25f2237c 100644
> --- a/builtin/gc.c
> +++ b/builtin/gc.c
> @@ -222,7 +222,7 @@ static const char *lock_repo_for_gc(int force,  
> pid_t* ret_pid)
> 			time(NULL) - st.st_mtime <= 12 * 3600 &&
> 			fscanf(fp, "%"PRIuMAX" %127c", &pid, locking_host) == 2 &&
> 			/* be gentle to concurrent "gc" on remote hosts */
> -			(strcmp(locking_host, my_host) || !kill(pid, 0));
> +			(strcmp(locking_host, my_host) || !kill(pid, 0) || errno ==  
> EPERM);
> 		if (fp != NULL)
> 			fclose(fp);
> 		if (should_exit) {
> -- 
> 1.8.5.2
>

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