On Wed, 28 Oct, at 09:12:27AM, Saurabh Sengar wrote:
> replace GFP_KERNEL with GFP_ATOMIC, as code while holding a spinlock
> should be atomic
> GFP_KERNEL may sleep and can cause deadlock, where as GFP_ATOMIC may
> fail but certainly avoids deadlock
>
> Signed-off-by: Saurabh Sengar <[email protected]>
> ---
> drivers/firmware/efi/vars.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
> index 70a0fb1..d4eeebf 100644
> --- a/drivers/firmware/efi/vars.c
> +++ b/drivers/firmware/efi/vars.c
> @@ -322,10 +322,11 @@ static unsigned long var_name_strnsize(efi_char16_t *variable_name,
> * disable the sysfs workqueue since the firmware is buggy.
> */
> static void dup_variable_bug(efi_char16_t *str16, efi_guid_t *vendor_guid,
> - unsigned long len16)
> + unsigned long len16, bool atomic)
> {
> size_t i, len8 = len16 / sizeof(efi_char16_t);
> char *str8;
> + int gfp_mask;
>
> /*
> * Disable the workqueue since the algorithm it uses for
> @@ -334,7 +335,12 @@ static void dup_variable_bug(efi_char16_t *str16, efi_guid_t *vendor_guid,
> */
> efivar_wq_enabled = false;
>
> - str8 = kzalloc(len8, GFP_KERNEL);
> + if (atomic)
> + gfp_mask = GFP_ATOMIC;
> + else
> + gfp_mask = GFP_KERNEL;
> +
> + str8 = kzalloc(len8, gfp_mask);
> if (!str8)
> return;
>
> @@ -408,7 +414,7 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
> if (duplicates &&
> variable_is_present(variable_name, &vendor_guid, head)) {
> dup_variable_bug(variable_name, &vendor_guid,
> - variable_name_size);
> + variable_name_size, atomic);
> if (!atomic)
> spin_lock_irq(&__efivars->lock);
It's slightly winding code, but if you look at the callers of
efivar_init() you'll see that none of them set both 'atomic' and
'duplicates', so dup_variable_bug() will never be called while holding
a spinlock.
Or am I missing something?
>It's slightly winding code, but if you look at the callers of
>efivar_init() you'll see that none of them set both 'atomic' and
>'duplicates', so dup_variable_bug() will never be called while holding
>a spinlock.
>Or am I missing something?
I was assuming that there could be a possibility when both 'atomic' and 'duplicates' are set.
If both can never be set, then this patch does not make any sense, you are correct.
Thank you for review