Re: [alsa-devel] [PATCH] ALSA: emu10k1: don't deadlock in proc-functions

10 Apr 2015

At Thu, 9 Apr 2015 23:42:15 +0200,
Michael Gernoth wrote:
...
The functions snd_emu10k1_proc_spdif_read and snd_emu1010_fpga_read
acquire the emu_lock before accessing the FPGA. The function used
to access the FPGA (snd_emu1010_fpga_read) also tries to take
the emu_lock which causes a deadlock.
Remove the outer locking in the proc-functions (guarding only the
already safe fpga read) to prevent this deadlock.
Signed-off-by: Michael Gernoth michael@gernoth.net
Oh, this is a really old bug.  Thanks for spotting out.
Applied now with additional fixes (removing superfluous flags
variables causing compile warnings).
Takashi
...

sound/pci/emu10k1/emuproc.c | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/sound/pci/emu10k1/emuproc.c b/sound/pci/emu10k1/emuproc.c
index 2ca9f2e..415d23c 100644
--- a/sound/pci/emu10k1/emuproc.c
+++ b/sound/pci/emu10k1/emuproc.c
@@ -245,27 +245,19 @@ static void snd_emu10k1_proc_spdif_read(struct snd_info_entry *entry,
   u32 rate;
if (emu->card_capabilities->emu_model) {

spin_lock_irqsave(&emu->emu_lock, flags);

snd_emu1010_fpga_read(emu, 0x38, &value);
spin_unlock_irqrestore(&emu->emu_lock, flags);

if ((value & 0x1) == 0) {
	spin_lock_irqsave(&emu->emu_lock, flags);
snd_emu1010_fpga_read(emu, 0x2a, &value);
snd_emu1010_fpga_read(emu, 0x2b, &value2);


	spin_unlock_irqrestore(&emu->emu_lock, flags);
rate = 0x1770000 / (((value << 5) | value2)+1);	
snd_iprintf(buffer, "ADAT Locked : %u\n", rate);

} else {
	snd_iprintf(buffer, "ADAT Unlocked\n");
}
spin_lock_irqsave(&emu->emu_lock, flags);

snd_emu1010_fpga_read(emu, 0x20, &value);
spin_unlock_irqrestore(&emu->emu_lock, flags);

if ((value & 0x4) == 0) {
	spin_lock_irqsave(&emu->emu_lock, flags);
snd_emu1010_fpga_read(emu, 0x28, &value);
snd_emu1010_fpga_read(emu, 0x29, &value2);


	spin_unlock_irqrestore(&emu->emu_lock, flags);
rate = 0x1770000 / (((value << 5) | value2)+1);	
snd_iprintf(buffer, "SPDIF Locked : %d\n", rate);

} else {

@@ -415,9 +407,7 @@ static void snd_emu_proc_emu1010_reg_read(struct snd_info_entry *entry,
   snd_iprintf(buffer, "EMU1010 Registers:\n\n");
for(i = 0; i < 0x40; i+=1) {

spin_lock_irqsave(&emu->emu_lock, flags);

snd_emu1010_fpga_read(emu, i, &value);
spin_unlock_irqrestore(&emu->emu_lock, flags);

snd_iprintf(buffer, "%02X: %08X, %02X\n", i, value, (value >> 8) & 0x7f);
}

}
2.1.4

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Re: [alsa-devel] [PATCH] ALSA: emu10k1: don't deadlock in proc-functions

Takashi Iwai

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