linux-toradex.git/kernel/irq/proc.c, branch v6.19

genirq/proc: Fix race in show_irq_affinity()

2025-10-31T21:30:05+00:00

Reading /proc/irq/N/smp_affinity* races with irq_set_affinity() and
irq_move_masked_irq(), leading to old or torn output for users.

After a user writes a new CPU mask to /proc/irq/N/affinity*, the syscall
returns success, yet a subsequent read of the same file immediately returns
a value different from what was just written.

That's due to a race between show_irq_affinity() and irq_move_masked_irq()
which lets the read observe a transient, inconsistent affinity mask.

Cure it by guarding the read with irq_desc::lock.

[ tglx: Massaged change log ]

Signed-off-by: Muchun Song 
Signed-off-by: Thomas Gleixner 
Link: https://patch.msgid.link/20251028090408.76331-1-songmuchun@bytedance.com

genirq: Consistently use '%u' format specifier for unsigned int variables

2025-05-13T07:43:32+00:00

There are three cases in the genirq code when the irq, as an unsigned
integer variable, is converted to text representation by sprintf().
In two cases it uses '%d' specifier which is for signed values. While
it's not a problem right now, potentially it might be in the future
in case too big (> INT_MAX) number will appear there.

Consistently use '%u' format specifier for @irq which is declared as
unsigned int in all these cases.

Signed-off-by: Andy Shevchenko 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/20250509154643.1499171-1-andriy.shevchenko@linux.intel.com

genirq/proc: Switch to lock guards

2025-05-07T07:08:11+00:00

Convert all lock/unlock pairs to guards and tidy up the code.

No functional change.

Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/all/20250429065420.373998838@linutronix.de

genirq/proc: Add missing space separator back

2024-12-03T13:59:34+00:00

The recent conversion of show_interrupts() to seq_put_decimal_ull_width()
caused a formatting regression as it drops a previosuly existing space
separator.

Add it back by unconditionally inserting a space after the interrupt
counts and removing the extra leading space from the chip name prints.

Fixes: f9ed1f7c2e26 ("genirq/proc: Use seq_put_decimal_ull_width() for decimal values")
Reported-by: Geert Uytterhoeven 
Signed-off-by: Thomas Gleixner 
Tested-by: Geert Uytterhoeven 
Reviewed-by: David Wang <00107082@163.com>
Link: https://lore.kernel.org/all/87zfldt5g4.ffs@tglx
Closes: https://lore.kernel.org/all/4ce18851-6e9f-bbe-8319-cc5e69fb45c@linux-m68k.org

genirq/proc: Use seq_put_decimal_ull_width() for decimal values

2024-11-13T16:36:35+00:00

seq_printf() is more expensive than seq_put_decimal_ull_width() due to the
format string parsing costs.

Profiling on a x86 8-core system indicates seq_printf() takes ~47% samples
of show_interrupts(). Replacing it with seq_put_decimal_ull_width() yields
almost 30% performance gain.

[ tglx: Massaged changelog and fixed up coding style ]

Signed-off-by: David Wang <00107082@163.com>
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/20241108160717.9547-1-00107082@163.com

genirq: Switch to irq_get_nr_irqs()

2024-10-16T19:56:59+00:00

Use the irq_get_nr_irqs() function instead of the global variable
'nr_irqs'. Cache the result of this function in a local variable in
order not to rely on CSE (common subexpression elimination). Prepare
for changing 'nr_irqs' from an exported global variable into a variable
with file scope.

Signed-off-by: Bart Van Assche 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/20241015190953.1266194-22-bvanassche@acm.org

genirq/proc: Change the return value for set affinity permission error

2024-08-29T14:42:06+00:00

Currently, when the affinity of an irq cannot be set due to lack of
permission, the write_irq_affinity() returns the error code -EIO.

Change the return value to -EPERM as that reflects the cause of error
correctly.

Signed-off-by: Jeff Xie 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/20240826145805.5938-1-jeff.xie@linux.dev

genirq/proc: Use irq_move_pending() in show_irq_affinity()

2024-08-29T14:42:06+00:00

irq_move_pending() encapsulates irqd_is_setaffinity_pending() depending on
CONFIG_GENERIC_PENDING_IRQ.

Replace the open coded #ifdeffery with it.

Signed-off-by: Jinjie Ruan 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/20240829111522.230595-1-ruanjinjie@huawei.com

genirq/proc: Correctly set file permissions for affinity control files

2024-08-29T14:41:42+00:00

The kernel already knows at the time of interrupt allocation whether
affinity of an interrupt can be controlled by userspace or not.

It still creates all related procfs control files with read/write
permissions. That's inconsistent and non-intuitive for system
administrators and tools.

Therefore set the file permissions to read-only for such interrupts.

[ tglx: Massage change log, fixed UP build ]

Signed-off-by: Jeff Xie 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/20240825131911.107119-1-jeff.xie@linux.dev

genirq/proc: Simplify irqdesc::kstat_irqs handling further

2024-06-03T09:48:29+00:00

Interrupts which have no action and chained interrupts can be
ignored due to the following reasons (as per tglx's comment):

  1) Interrupts which have no action are completely uninteresting as
     there is no real information attached.

  2) Chained interrupts do not have a count at all.

So there is no point to evaluate the number of accounted interrupts before
checking for non-requested or chained interrupts.

Remove the any_count logic and simply check whether the interrupt
descriptor has the kstat_irqs member populated.

[ tglx: Adapted to upstream changes ]

Suggested-by: Thomas Gleixner 
Signed-off-by: Adrian Huang 
Signed-off-by: Thomas Gleixner 
Tested-by: Jiwei Sun 
Link: https://lore.kernel.org/r/20240515100632.1419-1-ahuang12@lenovo.com
Link: https://lore.kernel.org/lkml/87h6f0knau.ffs@tglx/