Le 09/06/2023 à 10:57, Walter Harms a écrit :
while we are here ....
perhaps INT_MAX from kernel.h ?
from include/vdso/limits.h
int deviation = (1 << 30) - 1;
I don't know the initial intent for this value, but it is not the same
as MAX_INT.
the part before looks a bit strange
if (ourport->info->has_divslot) {
unsigned long div = rate / req_baud;
/* The UDIVSLOT register on the newer UARTs allows us to
* get a divisor adjustment of 1/16th on the baud clock.
*
* We don't keep the UDIVSLOT value (the 16ths we
* calculated by not multiplying the baud by 16) as it
* is easy enough to recalculate.
*/
quot = div / 16;
baud = rate / div;
because
baud=rate/rate/req_baud = req_baud
In math yes. In integer computation, no.
rate = 20000
req_baud = 9600
div = rate / req_baud ==> 2
baud = rate / div; ==> 20000 / 2 = 10000
9600 <> 10000
I don't know if it is the intent, but it is the way it works.
And knowing that:
calc_deviation = req_baud - baud;
I guess that it is the way it is expected to work.
With your reasoning, calc_deviation would be always 0.
can this be simplyfied ? (or is the numeric required ?)
Homebrew abs() kernel.h has a abs() can we use it here ?
include/linux/math.h
if (calc_deviation < 0)
calc_deviation = -calc_deviation;
Ok, why not.
to the patch:
+ /*
+ * If we find a better clk, release the previous one, if
+ * any.
+ */
+ if (!IS_ERR(*best_clk))
+ clk_put(*best_clk);
the intentions are good. *best_clk is user supplied (and should be NULL)
??? Why should it be NULL?
There is only one caller, and the value id &clk, knowing that:
struct clk *clk = ERR_PTR(-EINVAL);
The code could be changed to have an initial NULL value, but it would'nt
bring that much added value, in my PoV.
It would only save a test which is just fine as-is.
filled & released in the next round but IMHO must be valid (is clk).
so no need to check. (ntl clk_put seems to handle NULL and ERR )
if (!clk || WARN_ON_ONCE(IS_ERR(clk)))
return;
My point with "if (!IS_ERR(*best_clk))" is to handle the initial
iteration when *best_clk is ERR_PTR(-EINVAL).
clk_put() can handle it, but it would WARN in the normal path, so it
sounds strange to me.
CJ
JM2C
wh
________________________________________
Von: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
Gesendet: Freitag, 9. Juni 2023 06:45:39
An: Krzysztof Kozlowski; Alim Akhtar; Greg Kroah-Hartman; Jiri Slaby; Thomas Abraham; Kukjin Kim
Cc: linux-kernel@xxxxxxxxxxxxxxx; kernel-janitors@xxxxxxxxxxxxxxx; Christophe JAILLET; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-samsung-soc@xxxxxxxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx
Betreff: [PATCH 2/2] tty: serial: samsung_tty: Fix a memory leak in s3c24xx_serial_getclk() when iterating clk
When the best clk is searched, we iterate over all possible clk.
If we find a better match, the previous one, if any, needs to be freed.
If a better match has already been found, we still need to free the new
one, otherwise it leaks.
Fixes: 5f5a7a5578c5 ("serial: samsung: switch to clkdev based clock lookup")
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
This patch is speculative. Review with care.
I think that some clk_put() are also missing somewhere else in the driver
but won't be able to investigate further.
---
drivers/tty/serial/samsung_tty.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index dd751e7010e3..c07877dd25fa 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -1488,10 +1488,18 @@ static unsigned int s3c24xx_serial_getclk(struct s3c24xx_uart_port *ourport,
calc_deviation = -calc_deviation;
if (calc_deviation < deviation) {
+ /*
+ * If we find a better clk, release the previous one, if
+ * any.
+ */
+ if (!IS_ERR(*best_clk))
+ clk_put(*best_clk);
*best_clk = clk;
best_quot = quot;
*clk_num = cnt;
deviation = calc_deviation;
+ } else {
+ clk_put(clk);
}
}
--
2.34.1
